Do you ever use rest mode whilst playing the game or do you always close the application first? Close first - no rest mode
Does the issue still occur after closing the application and relaunching it? Yes as soon as I travel to francia during 1st mission
Are you able to manually save your game? Yes only after reloading uncorrupted save otherwise no
How often does it happen? As soon as mission reaches dock in francia
How much playtime (in hours) have you lost if any? None - reload uncorrupted save and don't play siege of Paris
Do you own the Wrath of The Druids and/or Siege of Paris expansion? Yes both
If so does this issue only occur whilst playing the expansion content or do you also experience it on other maps in the game? Only on arriving in francia and once in England but could be unrelated might have something to do with putting the beserker guy on crew in ravensthorpe (happened previously)

Do you ever use rest mode whilst playing the game or do you always close the application first? - Never rest mode, only close application.
Does the issue still occur after closing the application and relaunching it? - Yes
Are you able to manually save your game? - No, only cloud save, like manual, auto or quick
How often does it happen? - Always
How much playtime (in hours) have you lost if any? - +50hrs
Do you own the Wrath of The Druids and/or Siege of Paris expansion? - Both, season pass
If so does this issue only occur whilst playing the expansion content or do you also experience it on other maps in the game? - always, all available masp in all available regions in that map.

@ubi-orion
‘Yes, I use bot rest mode and close application.
yes. The issue happens every 5 seconds or so.
‘no. I can not manually save my game.
‘it happens any time the game auto saves, or when I enter a fight with any human or animal enemy.
‘it’s hard to tell how many hours I’ve lost. Not sure how to measure that, or why it would matter. Your game has Ann issue with the most basic task ever. It doesn’t want to save. FIX IT!
I own both expansions. The issue happens everywhere.

Game still fecked getting the same failed to save error already lost progress had to re-do some of the ireland DLC you'd have thought the issue would have been fixed by now

I don't know if the team solved anything, but today after the Reda store was reset, all of a sudden Save started, manual, auto and quick. Check it out for yourself if it is for You, I finally started playing DLC Paris, played two missions and is working for now. Here my fingers are crossed, and I hope it is not temporary or accidental but that the problem is solved and after more than a month I can continue to play especially the new DLC ...