game stops download at 65%

Hey guys,

my pc won't download the rest of the game, it says download queued. As soon as I qlick on resume it loads a bit and then pops up with a message that reads

"an error occured while updating game (disc write error): F:\Steam\steamapps\downloading\403640\base\game3.resources"

Anyone know what to do? it's installing on my external HD that has about 400gb left of free space.

Also, I found this in my steam content log:

AppID 403640 update canceled : Failed updating depot 531332 while writing chunk, offset 4298758387 (Write Failed) (Disk write failure) "F:\Steam\steamapps\downloading\403640\base\game3.resources"

I'd be really grateful if anyone here could help me.