F53 just means that it isn't spinning as expected because of (usually worn brushers in old ones but obviously not in the 3-phase brushless version) , perhaps the speed sensor or some other problem. Just done a repair on a friends machine that uses 3-phase motor. I checked continuity of the motor windings, then the sensor on the end of the shaft (which is just a coil in which a magnet rotates - about 250ohms but not critical, then looked at the board no visible problems but checked the 4 bridge diodes, then a emitter/collector check on each of the IGBTs one was clearly different and shorted (the internal diode appeared to have failed), replaced the GB10NC60HD and all is now working! I did a thermal camera check with it working to ensure I had achieved a good thermal connection under the suface mount tab.