Agreed, the pads are not the problem and air sucked into the the MC is easily solved. MCs have been replaced with out the desired result. The Breva 1100 has the same rear caliper and as far as I know haven't has this problem, this points to the ABS. But a batch of defective caliper seals is not far fetched. I measured the caliper piston on my Breva and found them to be 28mm, so it may be worth trying to rebuild one with seals from a P28N Brembo caliper Brembo kit # 120.3973.10 . The P28N is a different style caliper but the seal may be the same. The length has to match ( height lying down). So, who's gonna give it a try? Be very careful taking the old seals out, just in case new ones don't match. Worse case you'd have to replace the caliper and if the bike is still under warranty you can submit a claim.
Maybe swapping the caliper with one from a buddies bike would be a better experiment. KTM and Cagiva used a similar floating Brembo caliper used on dual purpose models during the '90s, the PF2.28C, maybe a kit is available for this model.
Rafael