Music is not working with video, sometimes not at all

I am having a hard time with music. I added my photos and video. Then added music. The music cut off before the pics were all done, so I went to "fit to music". What happened was that each picture was changed to a duration of 23.5 secs each. Yikes, how boring. Each time I edited the time for each pic and retried playing the movie, the time per picture jumped back to 23.5 secs each. the music is under 4 minutes and I have a lot of pictures. Can someone shed some light on this? Thanks in advance.