Hey bro, unfortunately you found another bug, sorry about that.
I'll start fixing this problem tomorrow and let you know here as soon as it's resolved. I already have the programming to allow changing the BGM and the battle BGM by tags. I'll expand this to work under the conditions of battle on map, including being able to change the enemy and music during the battle, and also the victory music. I thought your suggestion was very good and I'll implement it.
I apologize for the bug, everything will be resolved in a few days!
Thank you for the report and for all the support!