Giovanni boldrin

Hello everyone, I'm an Italian amateur. Sorry for my not perfect English. I often follow your forums, where I find invaluable answers to the many inconveniences that we may encounter in our passion. I own several instruments: Vixen r200ss, Celestron 9.25, orion 80Ed, with equatorial mounts: Vixen New Atlux, Meade lx80, and an Orion StarSeeker IV ( skywatcher Stardiscovery). This last mount was given to me because with the electronic part not working. The hand control V4 works perfectly (I have tested it on other mounts), I changed the motherboard with a new one . Everything now works and responds to the commands of the keypad. I have only one big problem: once aligned, the mount in the goto does not find the objects because the motors start quickly but at a certain point they stop and the display shows "slewing .." this situation continues for quite a while and you still hear the engines spinning .. I tried to change power thank with a 5A power supply, I registered the clutches, updated the firmware but nothing has changed! Is there a problem with the encoders or the motors?