Silly question but should you be able to push the bike freewheeling when switched off or does it just drag the rear wheel as if in gear

this very much depends on the type of controller but I would say 98% sure it should have no drag ( I don t know anything about the T12 or what motor or controller they use ) , try disconnecting the motor wires.. is it still hard to push ? if not then its a big possibility that the controller is faulty..

Thanks