This recently happened to me. Well not ME ofcourse!!!! but one of my robots. An operator put decided one day that he was going to grease his Motoman UP6. So he went and got a grease gun with some general purpose grease and he started pumping, and pumping, and pumping.
He got all the axes. He then came and got me when the robot wouldn't move. There was an axis overload on every axis. After I figured out what happened I started to dismantle the robot.
There wasn't too much broken, but..... The U axis servo was completely filled with grease and..... there was so much pressure that the motor split right in half!! I noticed this after I saw grease dripping from the encoder end of the servo.