UPDATE:
I eventually found that my issue launching MP3 from MPT was with BT passthrough, and it was corrected by changing my BT adapter's driver from libusbK to WinUSB (also through Zadig).
I eventually found that my issue launching MP3 from MPT was with BT passthrough, and it was corrected by changing my BT adapter's driver from libusbK to WinUSB (also through Zadig).
Windows 10 Pro x64 | i7-9700K @ 4.6-5.0GHz | MSI Z370 Gaming Plus | MSI RX 5700 8GB Factory-OC | 16 GB DDR4-3000
