Edit: Forewarning, I replicated the scenario but I didn't get the same result The music worked as normal when I repeated this for a second time. I've always tried the order of operations as Crown Guardians and then wall crown vault if I've found one, instead of opposite order of operations when the bug occured. It doesn't take much effort on my part trying to replicate the bug whenever I come across a vault, so I'll keep trying.
For readability I'll refer to the wall-embedded crown vault (the crown vault blocks that you have to dig to that spawn bonus chests with extra goodies) as a wall crown vault.
Upon completing a wall crown vault within a crown vault, and then fighting the original Crown Guardians that are within the pillars, the event music from the wall crown vault with start again, playing on top of the music when you fight the pillar Crown Guardians. The music doesn't stop and persists between levels. I have no footage of the cause of the bug in action, just the aftermath.