Sure. The last time I used MapRunG prior to the problem was on 28th April and it was version 1.4.1 - I nearly always sync my watch with Garmin Express on the day of a run and that updates MapRunG if applicable. The last time I sync'd it in this way was on 10th June, and I don't recall any updates being done then. I ran with the watch on 16th June (not MapRun) but deleted the run and didn't sync, although the watch probably sync'd via my phone. Then the next time I ran was on 23rd June when the problem occurred.
As far as the error screen is concerned, I can reproduce that by starting MapRunG (with no event loaded), pressing the "return" button (rather than "start/stop" as stated in the message that appears if I wait longer), and then selecting "continue". My description was slightly inaccurate before; it's a white screen with "IQ" in blue and a "!" in a yellow circle above the Q. Pressing "return" again takes me back to the screen with IQ, run, etc, and selecting IQ then Maprun again starts the app as normal without changing the Id (so I'm not sure what I did differently before that caused a new Id to be generated).
Thanks - Our best diagnosis to date is that as we introduce new versions of MapRunG we use the latest version of Garmin system tools and software libraries. It appears that the transition to the upgraded system software on some watches has a few bumps, and then settles down.