It seems like each game experiences desyncs after a certain point, where it starts desyncing constantly every few hours/days without an end, making the run unplayable after that point. Some things we noticed across various runs: it never happened before the spanish civil war, the quickest happened not many days after the sp civil war firing, the last happened in 1940, it mostly happened in 1938/39.

The description of the desync lists many things, basically half the things that can be listed.

I will edit this if i remember more details.

Thanks :)