Fanuc 6m problem

Hi! We have an old Bulgarian MC 032 5 axis machine with a Fanuc 6m. It went well about 2 years ago and recently we started to get it to work. When I turn it on the 5th axis twitches for approx. a couple of dergees then stuck and the errors 401 and 450 appear. Arter the reset it appears in just several seconds. When the motor us unplugged everything is fine with no errors. I found and replaced a blown fuse on 5th axis, the wiring seem to be OK. The DC motor is turning freely and the brushes are also fine. I couldn't find any specialists on this machine, so any help will be appreciated! Thanks!