All in the title but I'll explain.
Not every torrent but quite a few especially if there are a small number of peers <10, but it has happened on very popular ones too 2000+ peers, get stuck after downloading the initial piece, I have been observing this bug for a number of years actually and many different pcs, but it just crossed my mind to report it now.
Basically, you'll start downloading a torrent or magnet and it will just get stuck on the first piece, if you click on the pieces tab you see the piece is complete but the torrent is jammed until you press stop and then start and then it resumes at full speed. This happens with the following windows disk cache settings:
[X] Override automatic cache size.... [<any value say 1024>]
[ ] Reduce memory usage when cache not needed
[X] Enable caching of disk writes
--[ ] Write out untouched blocks every two minutes
[ ] Write out finished blocks immediately
[X] Enable caching of disk reads
[ ] Turn off read caching if slow
[ ] Remove old blocks from cache
[X] Increase cache size when thrashing
If you check the box for "Write out untouched blocks every two minutes" torrents will resume instantly instead of using start stop, in fact if that box is checked this issue never occurs (I have never noticed it) but without it, it happens quite frequently that a torrent will be stuck indefinitely and never progress until you intervene with a stop and start.