v8.1.28
I'm getting the same error Unable to create clean copy of class de.javasoft.plaf.synthetica.ScalableFont
I'm not using any fonts other than the mapped "Dialog" font 
I did enable the "Use Condensed Font" after upgrading, maybe this is it??
I turned it off and re-opened my project in Designer, created a new Vision Window and added a Label, saved, and I STILL get the error??
com.inductiveautomation.ignition.common.xmlserialization.SerializationException: Error during serialization for property 'contentPane' on object '[FPMIWindow]Main Window'
at com.inductiveautomation.ignition.common.xmlserialization.serialization.DefaultObjectSerializationDelegate.serializeProperties(DefaultObjectSerializationDelegate.java:157)
at com.inductiveautomation.factorypmi.designer.xmlserialization.WindowDelegate.serialize(WindowDelegate.java:34)
at com.inductiveautomation.ignition.common.xmlserialization.serialization.XMLSerializationContext.serialize(XMLSerializationContext.java:53)
at com.inductiveautomation.ignition.common.xmlserialization.serialization.XMLSerializer.serialize(XMLSerializer.java:529)
at com.inductiveautomation.ignition.common.xmlserialization.serialization.XMLSerializer.serializeBinary(XMLSerializer.java:510)
at com.inductiveautomation.factorypmi.designer.workspace.WindowWorkspace.saveContainer(WindowWorkspace.java:1839)
at com.inductiveautomation.factorypmi.designer.workspace.WindowWorkspace.commitDesignable(WindowWorkspace.java:1540)
at com.inductiveautomation.factorypmi.designer.workspace.WindowWorkspace.commitAll(WindowWorkspace.java:1097)
at com.inductiveautomation.factorypmi.designer.model.VisionDesignerImpl.notifyProjectSaveStart(VisionDesignerImpl.java:622)
at com.inductiveautomation.ignition.designer.IgnitionDesigner.commitAll(IgnitionDesigner.java:1610)
at com.inductiveautomation.ignition.designer.IgnitionDesigner.handleSave(IgnitionDesigner.java:1375)
at com.inductiveautomation.ignition.designer.IgnitionDesigner$Handler.handleSaveAction(IgnitionDesigner.java:2827)
at com.inductiveautomation.ignition.designer.IgnitionDesigner$Handler$5.actionPerformed(IgnitionDesigner.java:2407)
at java.desktop/javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at java.desktop/javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at java.desktop/javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at java.desktop/javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at java.desktop/javax.swing.AbstractButton.doClick(Unknown Source)
at java.desktop/javax.swing.AbstractButton.doClick(Unknown Source)
at java.desktop/javax.swing.plaf.basic.BasicMenuItemUI$Actions.actionPerformed(Unknown Source)
at java.desktop/javax.swing.SwingUtilities.notifyAction(Unknown Source)
at java.desktop/javax.swing.JComponent.processKeyBinding(Unknown Source)
at java.desktop/javax.swing.JMenuBar.processBindingForKeyStrokeRecursive(Unknown Source)
at java.desktop/javax.swing.JMenuBar.processBindingForKeyStrokeRecursive(Unknown Source)
at java.desktop/javax.swing.JMenuBar.processBindingForKeyStrokeRecursive(Unknown Source)
at java.desktop/javax.swing.JMenuBar.processKeyBinding(Unknown Source)
at java.desktop/javax.swing.KeyboardManager.fireBinding(Unknown Source)
at java.desktop/javax.swing.KeyboardManager.fireKeyboardAction(Unknown Source)
at java.desktop/javax.swing.JComponent.processKeyBindingsForAllComponents(Unknown Source)
at java.desktop/javax.swing.JComponent.processKeyBindings(Unknown Source)
at java.desktop/javax.swing.JComponent.processKeyEvent(Unknown Source)
at java.desktop/java.awt.Component.processEvent(Unknown Source)
at java.desktop/java.awt.Container.processEvent(Unknown Source)
at java.desktop/java.awt.Component.dispatchEventImpl(Unknown Source)
at java.desktop/java.awt.Container.dispatchEventImpl(Unknown Source)
at java.desktop/java.awt.Component.dispatchEvent(Unknown Source)
at java.desktop/java.awt.KeyboardFocusManager.redispatchEvent(Unknown Source)
at java.desktop/java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(Unknown Source)
at java.desktop/java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(Unknown Source)
at java.desktop/java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(Unknown Source)
at java.desktop/java.awt.DefaultKeyboardFocusManager.dispatchEvent(Unknown Source)
at java.desktop/java.awt.Component.dispatchEventImpl(Unknown Source)
at java.desktop/java.awt.Container.dispatchEventImpl(Unknown Source)
at java.desktop/java.awt.Window.dispatchEventImpl(Unknown Source)
at java.desktop/java.awt.Component.dispatchEvent(Unknown Source)
at java.desktop/java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.desktop/java.awt.EventQueue$4.run(Unknown Source)
at java.desktop/java.awt.EventQueue$4.run(Unknown Source)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.desktop/java.awt.EventQueue$5.run(Unknown Source)
at java.desktop/java.awt.EventQueue$5.run(Unknown Source)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.desktop/java.awt.EventQueue.dispatchEvent(Unknown Source)
at com.inductiveautomation.snap.swing.RibsEventQueue.dispatchEvent(RibsEventQueue.java:99)
at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.desktop/java.awt.EventDispatchThread.run(Unknown Source)
Caused by: com.inductiveautomation.ignition.common.xmlserialization.SerializationException: Error during serialization for property 'font' on object '[PMILabel]Label'
at com.inductiveautomation.ignition.common.xmlserialization.serialization.DefaultObjectSerializationDelegate.serializeProperties(DefaultObjectSerializationDelegate.java:157)
at com.inductiveautomation.factorypmi.designer.xmlserialization.DefaultComponentDelegate.serializeProperties(DefaultComponentDelegate.java:112)
at com.inductiveautomation.ignition.common.xmlserialization.serialization.DefaultObjectSerializationDelegate.serialize(DefaultObjectSerializationDelegate.java:184)
at com.inductiveautomation.ignition.common.xmlserialization.serialization.XMLSerializationContext.serialize(XMLSerializationContext.java:53)
at com.inductiveautomation.ignition.common.xmlserialization.serialization.DefaultObjectSerializationDelegate.writeCall(DefaultObjectSerializationDelegate.java:90)
at com.inductiveautomation.factorypmi.designer.xmlserialization.BasicContainerDelegate.serializeProperties(BasicContainerDelegate.java:120)
at com.inductiveautomation.factorypmi.designer.xmlserialization.BasicContainerDelegate.serialize(BasicContainerDelegate.java:45)
at com.inductiveautomation.ignition.common.xmlserialization.serialization.XMLSerializationContext.serialize(XMLSerializationContext.java:53)
at com.inductiveautomation.ignition.common.xmlserialization.serialization.DefaultObjectSerializationDelegate.writeCall(DefaultObjectSerializationDelegate.java:90)
at com.inductiveautomation.ignition.common.xmlserialization.serialization.DefaultObjectSerializationDelegate.writeCall(DefaultObjectSerializationDelegate.java:77)
at com.inductiveautomation.ignition.common.xmlserialization.serialization.DefaultObjectSerializationDelegate.doProperty(DefaultObjectSerializationDelegate.java:134)
at com.inductiveautomation.ignition.common.xmlserialization.serialization.DefaultObjectSerializationDelegate.serializeProperties(DefaultObjectSerializationDelegate.java:155)
... 62 more
Caused by: com.inductiveautomation.ignition.common.xmlserialization.SerializationException: Unable to create clean copy of class de.javasoft.plaf.synthetica.ScalableFont
at com.inductiveautomation.ignition.common.xmlserialization.serialization.XMLSerializer.getCleanCopy(XMLSerializer.java:595)
at com.inductiveautomation.ignition.common.xmlserialization.serialization.XMLSerializationContext.getCleanCopy(XMLSerializationContext.java:75)
at com.inductiveautomation.ignition.common.xmlserialization.serialization.DefaultObjectSerializationDelegate.serializeProperties(DefaultObjectSerializationDelegate.java:147)
at com.inductiveautomation.ignition.common.xmlserialization.serialization.DefaultObjectSerializationDelegate.serialize(DefaultObjectSerializationDelegate.java:184)
at com.inductiveautomation.ignition.common.xmlserialization.serialization.XMLSerializationContext.serialize(XMLSerializationContext.java:53)
at com.inductiveautomation.ignition.common.xmlserialization.serialization.DefaultObjectSerializationDelegate.writeCall(DefaultObjectSerializationDelegate.java:90)
at com.inductiveautomation.ignition.common.xmlserialization.serialization.DefaultObjectSerializationDelegate.writeCall(DefaultObjectSerializationDelegate.java:77)
at com.inductiveautomation.ignition.common.xmlserialization.serialization.DefaultObjectSerializationDelegate.doProperty(DefaultObjectSerializationDelegate.java:134)
at com.inductiveautomation.ignition.common.xmlserialization.serialization.DefaultObjectSerializationDelegate.serializeProperties(DefaultObjectSerializationDelegate.java:155)
... 73 more
Ignition v8.1.28 (b2023060110)
Java: Azul Systems, Inc. 11.0.18
Edit:
for some reason, when I drag on a label and don't change the font, it's telling me it's "Dialog, Plain, 19" which is odd. Usually the default font size is 16pt? or 12pt? can't remember. When I change it to 16pt, the font size is larger than the original "size 19pt"... And after changing the font size (nothing else), it now saves. I really don't want to have to set the font of every single text component in all of my Windows/Templates... 
Edit2:
This is a button I dragged on, only change was to add a script:
and after literally just clicking on the dropdown arrow beside the Font property and clicking OK (no changes to any of the values)
