Kelsey Hayes Pulling Problem

Every time I have seen this problem, it's been the opposite side. I have not seen a tire do this, but I have seen a tire create the pull in the first place, and braking would aggravate it.
So yeah, swap tires first, then dig into the other side. It may just be a pad hanging up or a contaminated pad. Leave the right for last; it is obviously working.
This assumes the combination valve is correctly plumbed,and correctly working.