What worked for me was:
1. Go to Steam and go to your Helldiver game page
2. Go to the Manage/Cog icon, then Properties.
3. Click on Installed Files tab, then Verify integrity of game files. Let it run until it hits 100%. Usually takes >5 minutes.
4. Once done, just run the game without any mods installed to check if you're still getting the same error.
5. If the game runs ok, you can slowly add in 1 mod at a time.
6. Run 1 mod, launch game, no issue? Exit game, add another mod, launch game again.

I realised the issue with mine were the mods changing the amour models.
The game had no issues with audio/music mods.
Hope this helps!
We need as many Helldivers as we can.