Hey mate,
One suggestion I do have is check your battery optimisation settings, make sure they’re set to unrestricted for both Bluetooth and Bluetooth MIDI service app. i hope this fixes it.
Also check that this isn’t an issue with the device you’re connecting to your phone by testing them on another device (laptop, tablet, phone, etc).
If you still continue to have issues, I’d submit a bug report via settings > system > feedback.
