Okay, re-read the VCDS scan. Module J104 is indeed the ABS module, but the faults relate to the parking brake (right), specifically implausible signal and electrical failure. When the caliper was swapped out for a pattern part then genuine Audi, did it come with brand new plug and play EPB, or was the original EPB swapped over? ABS module seems unlikely, why just rear right, why not left? They are sensitive bits of kit, especially if they have been ‘jumped’ in a previous life to change pads with separate 12v source. VCDS has specific procedure for pad changing, plus it’s recommended to keep power to the battery with a trickle charge on pad swap over. This may or may not be useful, but I rebuilt the brakes on my B8 A4 Allroad. Audi don’t even stock parts for rebuild, apart from a caliper square seal and dust boot. Budweg kits (Autodoc) come with ‘o’ rings that seal the caliper splindle on both sides. This is what stops water ingress. You need long needle nose circlip pliers to swap out. If you’ve got a new Audi OE brake caliper, then this will be fine. However if old EPB was simply bolted on, who knows? It’s held on with Torx screws. Another open given you have VCDS is to post the log on RossTech forum if you haven’t already done so. Looked on LLL parts for the parking brake module but no luck. That’s not to say it isn’t there though. Appreciate that some models of A3 use the ABS module.