Just FYI, it has always been a “no go” to create GUI windows inside a timer block.
If you try with message boxes, there is a runaway with multiple message boxes being created until the user must use Task Manager to kill the SketchUp process.
P.S. - I thought we had discussed this (extension check) in a previous thread and advised you to use the AppObserver ?
EDIT - Okay, it wasn’t you, but you were a participant in both recent topic threads where TIG and I suggested using the AppObserver …