According to the manual, I think merchant block should return decline reason = +090 (merchant block) instead of +064 (unknown).
I’ve checked program aus008q. It will check if aummd-block-action = ‘1’, then it will move decline reason = +090 for merchant block.
I tried to find which program update flag ‘1’ to field aummd-block-action but I could not find any.
Please help to advise kha.