I have had Kowas for over 30 years. For the most part I have used TriX, Forma, Delta, and both Kodak and Fuji color without issue. But when I use HP 5, the film advances to frame 1, fires and returns the mirror, on the second exposure the mirror does not return and the film advance is locked up. As soon as I remove the film the mirror returns. I have not tired PF4 or plus x, but only seems to cause a problem with HP5. Any ideas what is going on?