Since you just had the bearings repacked, I would take the drums off and confirm that grease hasn't gotten onto the linings. Maybe 1 or more warped drums? You might try lifting one wheel at a time off the ground (if you know how to do it correctly) and checking to see if all 4 brakes are working properly.
We had grease in our brakes on our first TT from brand new and the brakes were really grabbing/pulsating when applied and the tires would skid on gravel surfaces. Took the dealer 12 months until they finally took it all apart and completely rebuilt all 4 brakes due to grease on the linings plus they replaced all of the drums because they were warped. We were told it was our brake controller and had it replaced for over $300 with a Prodigy P3 while on the Oregon Coast, but it made no difference.