File being blocked from folder

I have a rather odd issue, a game I was playing somehow managed to trigger BitDefender (the game is legit, there is nothing wrong with it, thousands of others are using it without issue, it is on steam and other services). Bitdefender then decided to delete the main file, so I tried to get Steam to verify the integrity and replace the files. But steam keeps getting a Disk Write Error.

So after getting this a few times I found the folder where the file in question should be copied once re-downloaded. I can make files and folders in this location, I can copy other exe files into the folder, but the ONE file I NEED to go into the folder is denied access. Just this ONE file, any other file can be copied without issue.

I've had a look at a few "solutions" but I can't seem to find one that matches this. It could possible be something else blocking the file I guess, but given Bitdefender is my AV/security suite I'm leaning towards it blocking something. Tried updates and reboots etc as well. Any ideas would be more than welcome.