I believe the notation info SysEx messages sent out aren’t valid. I haven’t really looked at SysEx before, but was just implementing some bits in Arduino when I came across this (I may well be wrong!).
For a 2/4 signature, BB sends:
F0 7F 7F 03 04 02 18 08 F7
…but if the intent is for an immediate change I believe it should be sending the following (with an additional 2 bytes):
F0 7F 7F 03 02 04 04 02 18 08 F7
where 02 = immediate (or 42 to change at the next bar) and 04 is the number of bytes to follow
That’s my understanding from reading: http://www.somascape.org/midi/tech/spec.html#rusx_ni
This could explain sync issues with various loopers.