OPC tags don't always change value of the related OPC item


I created an OPC tag that is link to an item from my plc which was created with an OPC server. I pass this OPC tag to a pop up window. When I click on a button in the pop up window, I set the OPC tag to True with this line of code in the script :

event.source.parent.fvnr.commands.man_start_stop = True

The value in the PLC changes most of the time, but sometime, it dosen't. I need to close the pop up window, then re-open it. What is the issue? Is there a better way to change the value of the item?

Thank you!

What is man_start_stop? Is this a custom property with a bidirectional binding to your OPC tag? Perhaps it would be better to use system.tag.writeBlocking, and write the value directly to the tag instead of relying on the binding.