I know it would help if I create a small example to reproduce the error, but for now this explanation should do:
I use a timer that waits a couple of seconds to then perform a http-request using Sketchup::Http::Request in order to check if a new version of the extension is available. If that is the case I create a UI::Notification to inform the user that a new version is available and ask him/her if he/she wishes to update. Both a click on accept or on dismiss cause a bugsplat in SketchUp 2019. The same code causes no trouble in SketchUp 2018 nor 2017.
I have sent a bugsplat report.
Anyone else having troubles with UI::Notification in 2019?
Could someone from the SketchUp team perhaps take a look at the bugsplat report? It contains my name and the same description as mentioned here.