I am using the app for years now, and I am very sattisfied with the product.
However since a couple of days ago, the track order was messed up in quite an eratic way. With eratic, I mean
behaviour different from album to album
behaviour different from try to try (especially, when rebuilding the library between trys)
sequence of track listing different from order in which the tracks are played
no pattern visible
To rule out, that my library was simply to big (ca 17000 songs on the phone), I deleted all music and put 3 albums freshly on the phone: 2 Operas with