Ah! At last! I was beginning to think I was the only one who had that problem.
While making a large slideshow (about 250 photos), I found that when I put a short ending video at the end, the sound of the video appeared about 5 secs before the actual clip. Up til then I hadn't noticed anything was wrong. I tried going back through the slides to see where the problem was in case there was a dodgy transition or something. No matter where I inserted the small video the sound was still out of sync. I also noticed that some transitions didn't start & finish when they were supposed to. Odd...
Then I looked at the duration of the slides. I had selected magic motion on them all & PD had altered the length of the duration I initially had. That was ok bit I also noticed it had set a weird time of something like 7:13 secs. Just for the heck of it I retyped the time in again (at 7:13) & when I ok'd it, I thought I noticed the length of the slide change ever so slightly. I then zoomed in on another slide to fit the whole length of the timeline so I could get a better look. I retyped the same duration & when I ok'd it this time I could definitely see a change in the length of the slide. Over the course of 20 mins this made the sound get so far out.
I then went through the whole slideshow & changed them all to 7 secs. At this point I wished there was a way to change the duration of all selected... Are you listening Cyberlink?
Low & behold when I inserted the small video at the end, the sound matched perfectly! Perhaps this was why PD also decided to crash at times. Maybe it was trying to sync things that were out of whack, because I also noticed it didn't crash after this fix.
So that was what I found. If you use magic motion & you find the sound gets out of sync, have a look at re-doing the durations. It worked for me.
Let me know if you have a similar problem & if this works for you.
Regards,
Peter B.