this seems very odd. i haven’t had any midi issues yet (especially via jack).
my suggestions of things you could try:
- try powering the device from a different powersource (maybe a usb powerbank)
- try flashing the firmware fresh (maybe even via emergency flash)
- backup your card and then format the sd card (FAT32) and put everything back onto it
Does the same issue happen even if you use MIDI over USB?
if none of this helps, i would say you might have a faulty unit. At that point i would contact customer support.
Hope that helps and let us know if there is anything else we can do to help! 