This is likely not GD related but more Steam related. I use Item Assistant with Steam cloud storage disabled for reference. Played V1.2 last night no problem. This morning, Steam had automatically re-enabled cloud storage for GD before or after downloading the hotfix (little icon popped up next to GD in the games list), then got stuck on the “Steam content file locked” error message and locked out the game.
I had to clear the Steam download cache, close IA, disable cloud storage again, and restart the computer before the error cleared up. Probably not a widespread issue, but posting in case anyone else has the issue.
Edit: Turns out it’s just Item Assistant. Closing it out and restarting Steam clears the error. Don’t know why cloud save enabled itself though.