# Perspective - Unexpected problem unregistering listener from session event bus **URL:** \ **Category:** Ignition\ **Tags:** perspective\ **Created:** [October 13, 2020, 2:01pm UTC](https://forum.inductiveautomation.com/t/perspective-unexpected-problem-unregistering-listener-from-session-event-bus/39636 "2020-10-13T14:01:30Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![Devin](https://avatars.discourse-cdn.com/v4/letter/d/278dde/32.png) [@Devin](https://forum.inductiveautomation.com/u/Devin)\ **Post date:** [October 13, 2020, 2:01pm UTC](https://forum.inductiveautomation.com/t/perspective-unexpected-problem-unregistering-listener-from-session-event-bus/39636/1 "2020-10-13T14:01:30Z")
Hi all, I'm getting the below error in my gateway logs referring to an expression binding on a Perspective label component. It seems to populate the error anytime I have the page active. Wondering if anyone has seen this before? The expression binding on props.text is: > {view.params.Label} + ": " + {view.params.Value} + " " + {view.params.Units} I'm currently running 8.1 RC2 so it's possible it is related to that. > Unexpected problem unregistering listener from session event bus > > java.lang.IllegalArgumentException: missing event subscriber for an annotated method. Is com.inductiveautomation.perspective.gateway.binding.expression.ExpressionBindingTagListener$SessionEventListener@64bd4089 registered? > at com.google.common.eventbus.SubscriberRegistry.unregister(SubscriberRegistry.java:111) > at com.google.common.eventbus.EventBus.unregister(EventBus.java:201) > at com.inductiveautomation.perspective.gateway.binding.expression.ExpressionBindingTagListener.shutdown(ExpressionBindingTagListener.java:69) > at com.inductiveautomation.ignition.common.expressions.BoundTagExpression.shutdown(BoundTagExpression.java:102) > at com.inductiveautomation.ignition.common.expressions.AbstractExpression.shutdown(AbstractExpression.java:52) > at com.inductiveautomation.ignition.common.expressions.AbstractExpression.shutdown(AbstractExpression.java:52) > at com.inductiveautomation.ignition.common.expressions.FunctionExpression.shutdown(FunctionExpression.java:56) > at com.inductiveautomation.ignition.common.expressions.AbstractExpression.shutdown(AbstractExpression.java:52) > at com.inductiveautomation.ignition.common.expressions.FunctionExpression.shutdown(FunctionExpression.java:56) > at com.inductiveautomation.perspective.gateway.binding.PerspectiveExpression.shutdown(PerspectiveExpression.java:174) > at com.inductiveautomation.perspective.gateway.binding.expression.ExpressionBinding.shutdown(ExpressionBinding.java:61) > at com.inductiveautomation.perspective.gateway.model.AbstractBindingHarness.shutdown(AbstractBindingHarness.java:161) > at com.inductiveautomation.perspective.gateway.model.DesignerPageModel$BindingPreviewSupport.modify(DesignerPageModel.java:132) > at com.inductiveautomation.perspective.gateway.model.DesignerPageModel$DesignerHandlers.lambda$new$8(DesignerPageModel.java:310) > at com.inductiveautomation.ignition.common.util.ExecutionQueue$PollAndExecute.run(ExecutionQueue.java:210) > at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) > at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) > at java.base/java.lang.Thread.run(Unknown Source) ---
**Author:** ![richard1](https://avatars.discourse-cdn.com/v4/letter/r/50afbb/32.png) [@richard1](https://forum.inductiveautomation.com/u/richard1)\ **Post date:** [January 18, 2021, 6:45pm UTC](https://forum.inductiveautomation.com/t/perspective-unexpected-problem-unregistering-listener-from-session-event-bus/39636/2 "2021-01-18T18:45:52Z")
Same issue on my system for any screen object that has logic tied to it such as if this then “Running” else “Stopped” or tag + “:” +tag It look like this error occurs if the same tag is used in a binding expression more then once such as Tag1/Tag1 or Tag1+Tag2/Tag1 ---
**Author:** ![ShaneH](https://avatars.discourse-cdn.com/v4/letter/s/3e96dc/32.png) [@ShaneH](https://forum.inductiveautomation.com/u/ShaneH)\ **Post date:** [March 10, 2021, 9:31pm UTC](https://forum.inductiveautomation.com/t/perspective-unexpected-problem-unregistering-listener-from-session-event-bus/39636/3 "2021-03-10T21:31:44Z")
I had this same issue, with a binding that had multiple references to the same tag. Reorganizing the binding expression to only reference the tag once seemed to have made the problem go away. ---
**Author:** ![gottsche](https://avatars.discourse-cdn.com/v4/letter/g/ac91a4/32.png) [@gottsche](https://forum.inductiveautomation.com/u/gottsche)\ **Post date:** [April 15, 2021, 8:18am UTC](https://forum.inductiveautomation.com/t/perspective-unexpected-problem-unregistering-listener-from-session-event-bus/39636/4 "2021-04-15T08:18:32Z")
We stumbled across the same problem in version 8.1.4 when having multiple references to the same tag on a Perspective component. Is this the intended behavior or is this a bug? Why do expressions work differently here than they work somewhere else? ---
**Author:** ![jramirez3](https://avatars.discourse-cdn.com/v4/letter/j/a183cd/32.png) [@jramirez3](https://forum.inductiveautomation.com/u/jramirez3)\ **Post date:** [June 15, 2021, 3:47pm UTC](https://forum.inductiveautomation.com/t/perspective-unexpected-problem-unregistering-listener-from-session-event-bus/39636/5 "2021-06-15T15:47:13Z")
Yep, i’m running into the same issue. ---
**Author:** ![nskoog](https://avatars.discourse-cdn.com/v4/letter/n/ebca7d/32.png) [@nskoog](https://forum.inductiveautomation.com/u/nskoog)\ **Post date:** [October 25, 2021, 4:58pm UTC](https://forum.inductiveautomation.com/t/perspective-unexpected-problem-unregistering-listener-from-session-event-bus/39636/6 "2021-10-25T16:58:11Z")
Same issue here, with version 8.1.9 ---
**Author:** ![BluegelMarius](https://avatars.discourse-cdn.com/v4/letter/b/e9c0ed/32.png) [@BluegelMarius](https://forum.inductiveautomation.com/u/BluegelMarius)\ **Post date:** [November 15, 2021, 10:15am UTC](https://forum.inductiveautomation.com/t/perspective-unexpected-problem-unregistering-listener-from-session-event-bus/39636/7 "2021-11-15T10:15:43Z")
We have the same issue with Ignition 8.1.7. Is the IA team working on resolving this or is this an expected behaviour? If it is, is there a reference in the user manual? ---
**Author:** ![Kowa92](https://avatars.discourse-cdn.com/v4/letter/k/779978/32.png) [@Kowa92](https://forum.inductiveautomation.com/u/Kowa92)\ **Post date:** [January 22, 2022, 4:09pm UTC](https://forum.inductiveautomation.com/t/perspective-unexpected-problem-unregistering-listener-from-session-event-bus/39636/8 "2022-01-22T16:09:42Z")
Hi, no one news about it? Thx ---
**Author:** ![caleb.clark](https://avatars.discourse-cdn.com/v4/letter/c/a6a055/32.png) [@caleb.clark](https://forum.inductiveautomation.com/u/caleb.clark)\ **Post date:** [March 31, 2022, 1:26am UTC](https://forum.inductiveautomation.com/t/perspective-unexpected-problem-unregistering-listener-from-session-event-bus/39636/9 "2022-03-31T01:26:33Z")
This issue is still persisting. Using Version 8.1.14. Is this going to be addressed by someone from [@inductiveautomation](https://forum.inductiveautomation.com/groups/inductiveautomation)? ---
**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\ **Post date:** [March 31, 2022, 1:29am UTC](https://forum.inductiveautomation.com/t/perspective-unexpected-problem-unregistering-listener-from-session-event-bus/39636/10 "2022-03-31T01:29:23Z")
I think I found an issue describing this and the dev work is in progress. I’ll add this thread to the issue. ---
**Author:** ![zacharyw.larson](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/zacharyw.larson/32/23749_2.png) [@zacharyw.larson](https://forum.inductiveautomation.com/u/zacharyw.larson)\ **Post date:** [July 21, 2022, 7:48pm UTC](https://forum.inductiveautomation.com/t/perspective-unexpected-problem-unregistering-listener-from-session-event-bus/39636/11 "2022-07-21T19:48:37Z")
I just started to see this issue. I am on 8.1.0 though. Does it stop your reads? I get the issue in the logs, but the binding seems to be working. ---
**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\ **Post date:** [July 21, 2022, 7:53pm UTC](https://forum.inductiveautomation.com/t/perspective-unexpected-problem-unregistering-listener-from-session-event-bus/39636/12 "2022-07-21T19:53:26Z")
AFAIK this is resolved as of 8.1.17. I don’t think it made your bindings stop working, it was more a bookkeeping issue when shutting them down, I think.