The other threads are getting long, so I thought I would start a new one as I have not seen this issue reported yet.
Three days ago, in the alldayvideotenseconds folder, I had over 9,000 jpgs

starting about the time I started upgrading the moviemaker software. I got the feeling that the files are not erased after the tensecond video is made. I erased those files and today again there were many more old files. I have always had a few stragglers (20 or so) left over from the previous day in the alldayvideo folder that I erase daily, but I hadn't had any issues in the alldayvideotenseconds folder.
I do like the current moviemaker much better that the old. It is much easier on the computer and the videos are much smoother.
WD V: 10.37P
Moviemaker V: 2.5 (currently, but the orphaned jpgs dated back to many previous versions)