classic motorcycle forum

I have had the rear brake on a 1959 Constellation professionally relined but on reassembly the wheel appears to lock up when spun.  It feels just as if the bike has jumped into gear but the chain is not even connected so it can't be that !  I have had the relining checked and am assured that all is fine with that and the hub so am now at a loss as to what is happening.     A colleague has suggested that it could be something to do with the the torque arm but could not explain further.   Has anyone got any ideas please ?