CaptainSyrup wrote:I think i saw this problem once aswell. Some Custom Music even when it's mp3 format doesn't play in smbx then for some reasons. Sometimes it takes a bit longer and sometimes it starts automatic after enabling the custom button.
I had this problem as well. I was trying to use certain music for a Bowser battle but it refused to play. I found out that it was because sometimes the bit rate of the music might be too high, and if the bit rate is too high then the music won't play in SMBX. Lowering the bit rate will allow it to play in SMBX.