This "feature" appears to have issues due to the way filespace is allocated, as several other threads reporting problems with it show. I think that is possibly causing at least some of these errors.
0.3.17 has the same problem. Apparently a possible patch has been posted in this thread:
Forum=Major Problems, Thread=IO Error using pre-allocate and priority list
but I have no idea how to add that patch to the program.
(too bad I can't just link to the thread so you don't have to dig thru the forum for it, but links are apparently not allowed in posts)