There are always a few files that fail to validate on Steam.

This is completely normal!
These files are Authentication Files that are generated and sent to our backend every time you launch the game.

If however, you have 10 or more files that constantly need to validate, please try the following:

• Update Drivers
• Reinstall the Game
• Delete the content of the the Helldivers 2 Appdata folder (you can find the folder by pressing Windows + R and then typing "%appdata%" ) 
  Please be aware that this will reset all of your ingame settings

If you are still encountering issues with your game, please submit a ticket, and we will get round to helping you as soon as possible.