Musical scores stops playing in Premiere Elements 14

I am editing my videos taken with a Canon Powershot in Premiere Elements 14 and adding soundtracks from the Elements Library (sound effects and musical scores). In two different projects (+/- 30 min each), a musical score abruptly stops playing without any reason once I export the project, both in the exported file and in the project. If I change something to the length of the audio track, (e.g. shortening it to where the track stops playing or lenghtening it so that I can mute the part that I do not need), the place where it stops playing changes or another musical score at a different place in the project stops playing.

It is really annoying, since everything seems to be working fine when I add and adjust the soundtrack and it is first afterwards that the problem occurs. I have not noted the problem before trying to export the project a first time, although I checked that the end of each musical score did play.