getting same experience - been playing just fine for a week, last 2 days got very bad. The day before yesterday I saw a message about clearing out old saves to help stability, so I went through and did just that - things got way worse in one day.
Yesterday I pretty much wasted whole evening of play time because the mission I completed froze on getting back to argo screen after all the reports and apparently it didn't save progress when that happened - I was looking at Argo with no UI.
Not only did it break than, it somehow corrupted the game so that next time I started it, it froze on loading screen with the skull for 10 minutes.
Third time, the game actually loaded and freaked me out by telling me there was no campaign to Load - the button was greyed out and Continue did nothing.
Finally on the FOURTH time I restarted the game, it managed to see my save files and I discovered that the mission I spent an hour on didn't actually save.
GOG version with cloud saving disabled - their patch can't get here soon enough