I first noticed this on the Android version of the game, but it seems to persist in the PC version after importing my save from the Android. (Starting a brand new save produces the same exact result)
The closest instance of this is in the Nexus upon exiting Forest World. Upon return to the Nexus, Forest World’s theme will continue to play. This is the case in a few other areas, where no music transition occurs where expected (will update as I recall/find just to list a few examples)
Any reason why this would happen, and is there a fix? It’s not unplayable, but it does take away from some of the impact that the music is meant to give.