Sorting problems on 2 short YouTube MovieMaker videos

I've made about 10 simple YouTube MovieMaker videos over the last few years consisting of an audio track and a series of PowerPoint slides dropped in as jpegs to fit in with the audio track. I've just made two more short (10 minutes and 7 minutes) YouTube MovieMaker videos and am having some small problems. Although I have placed the jpegs in the right place, when I playback the videos to check everything is OK, in a couple of places the jpegs don't come up at the right times even though they have been placed in the correct place.

I need someone to get the two MovieMaker files and sort out the problem. This is a tiny job which should take less than an hour and it might need us to talk on the phone (Skype) so we can be sure everything has been sorted.

I attach a link to one of my previous simple videos so you can see how basic they are https://www.youtube.com/watch?v=s_upRjWhpd4&t=52s