I used to find similar with the Hypermotard, the brakes would feel awful and pulse sometimes, and the caliper pistons and bobbins would need cleaning to remove all the collected gunk.
It once failed an MOT because of "warped front disks". I told the tester that I would take it home and clean it, then bring it back but he laughed and said "you won't clean warped disks!".
How I laughed when I took it back an hour later and it passed
