The music in the resource packs has the same duration as the music in vanilla minecraft.
So if the music of the texture lasts longer than in vanilla minecraft it stops.

To execute the bug you have to install a texture that changes the music on the game discs and play it on the record player, and wait for it to stop (the texture's song must be longer than the vanilla one).

PS: The bug almost always happens in MCPE, in windows 10 there were some times that it didn't happen. I tried it with 3 texture packs and they all gave the same result.