Correction 2: The lag on research completion is multiplied by the amount of researched stuff added to recpies. Is the process that adds recipes a blocking one?

Ok correction of the last one - it just freezes for an obscene time frame of more than 10 minutes

Ok nevermind flatpak blaming, now it happened on Fluid Handling research finish:

It stopped happening outside of Steam flatpak. I'm blaming flatpak.

1. idling when an autosave hits with cursor over a building
2. freeze on autosave with 0% cpu activity, didn't unfreeze in the next half an hour (according to logs it freezes after the autosave)
3. lack of what happened
4. sometimes
5. once happened when screenshotting on gnome, once when pointing ...