[2022] Unable to revert to 1.4.4

Did you load your 1.4.4 Ironman save under 1.5 somehow?

When you revert game versions, you should delete at least the three 'cache' folders in the Documents/paradox interactive/ck3/ folder - does that help the crash on start of 1.4.4 ?  

Thanks; the clean reinstall I usually suggest for such issues would have worked too, I'm sure.

macdesktops said: I performed an Uninstall from Steam, and then re-installed 1.4.4. Presumably, that would have nuked the cache folders.

Not at all. Steam only deletes files it put there, not ones the game creates for itself.