Had that happen on a Jayfeather we used to own. I always check brakes and wheels for heat whenever I stop. All the bearings and brakes had been fine and well maintained. Then one day while on a long haul I pulled into a rest area and one wheel was warm- or more accurately put HOT!
I limped at very slow speeds 50 miles down the road and was able to get to a Camping World shop. They pulled the wheel and the brake shoe lining had completely shattered and lining material was wedging between the shoe frame and the wheel drum. Needless to say we found we then had the opportunity to install a new set of shoes and drums! Even though the old set was in pretty good shape we changed all the backing plates and brake assemblies on the rig. Never could figure why the shoe lining hung, but it all worked out OK.