@Kevin4fm Oh, believe me, I understand your logic. Why just these files, why just this site, why...
You would be surprised to know how often I hear those same questions when it comes to qBittorrent. Unfortunately that's the problem with bugs. They can be near impossible to pin down, without full knowledge of what actually causes them and what programming was done to create them. Not to mention the coding for different trackers handling different errors differently. Different .torrent creators creating torrent files differently, etc.
Is it possible it's not qB? Sure. But my bet is, it's qB. Wait for a new stable update for your system, and see if that fixes it. There may also be a setting somewhere in the client that can be switched on/off that could also affect just those few files. I'm no expert on clients, so I wouldn't know where to start looking.
Hopefully it won't be too frustrating for you either way. At least knowing it might just be a glitch, and it's really not affecting your uploading/downloading, will provide enough solace.