Random "File cannot be read" when reading from NAS

This only started when I upgraded to 1.5.2. It can happen at any point in time during the stream from the NAS. To make things even more random, here's what I noticed so far:
- This doesn't happen with files that I copied to the NAS from my old disks, only from files I added to the NAS through torrenting.
- If I move the preview cursor on the TV to one of those older files and allow Serviio to start playing the preview, and then move it back to the movie I was watching, I can get it to play.
- However this isn't 100% reliable. Sometimes it just refuses to play at all.
- Sometimes restarting the server on the PC helps, sometimes it makes no difference at all.