Ok, that is a bit strange. For me using my AR or A4 as midi clock master works equally good.
From the top of my mind stuff you can check:
- latest os on both machines.
- apart from having the midi clock send and recieve correctly setup make sure you have transport receive and send enabled as well
- check the advanced settings in the sequncer so you dont have like a 15 step pattern on one machine and 16 on the other and the master len and chng are equal or matching (like 32 on one and 64 on the other.)
- are you sending midi program changes my misstake to the A4?
- do you have a multi map on the A4 that responds to notes the pads of the AR sends?
- does the A4 go out of sync being a midi slave with other gear/software?