If the fix above doesn't work, try this.
One thing to try could be of course reinstalling the game. First i would try to verify the files on steam. Here's how to do it:
1. From the Library section, right-click on the game and select Properties from the menu.
2. Select the Local files tab and click the Verify integrity of game files... button.
3. Steam will verify the game's files - this process may take several minutes.
here is a gif from steam's own guide on how to do it: https://i.imgur.com/wWS80q1.gifv
If this doesn't work, i would recommend trying to reinstall the game. When you reinstall, remember to backup your save files since steam has no cloud saves on ETS2 according to my knowledge.
Edit: Of course the problems with your save could be a cause of a problem in the save game itself.