Hello, I think someone has had a similar problem, but not exactly the same.
With both 2.5 and 2.6 the music for both campaign and battles simply stops playing after a while. I have edited the music txt files and played around with a few ideas but nothing seems to work. after about three or four music tracks on CM and only two or three on BM the music still stops and refuses to play until an event occurs that re triggers it.
I imagine that the only file that affects music is the descr_sounds.music.txt so here is the one i have edited from the 0-turn campaign folder for Rome.
thanks in advance for any help.