I’ve been riding my first electric skateboard for about a week with no problem at all. At one point motor started to make weird noise. Once I turn it off and turn it on again, it wouldn’t make any noise. But it would start to make weird noise again when I hop on (also it lost a lot of torque. It wasnt able to push me fast). I went through other discussions and I suspected a short in phase wires. So I disassembled the motor to have a look but motor seemed perfectly fine (enamel coating didn’t strip off, phase wires were not touching)But since I opened up the motor, I taped around three phase wires where it comes out from the motor and I’ve added extra heat shrink on top of all the phase wires combined. Again with no load motor would work completely fine (apart from vibrating hideously at high rpm. I’m guessing it’s coming from dynamic unbalance) . When I’m on it, motor wouldn’t make noise until I pass about 6km/h speed. But torque is there this time as it was able to push me around. I’m really lost now guys. Your help will be appreciated 
1/ Is your belt and pulleys aligned? Loose belt?
2/ Are all bolts tightened? Both in motor and mounts, trucks, wheels etc.
if you have your motor apart may as well do a ohms test or a short circuit test. think you will find one of the coil phases is either broken or shorting. also check for magnet slip.
I’ll have to take it apart again but how can I perform those tests?
I believe that all the parts are in place.
for the ohm you will need a multimeter. dont have to take apart just unplug motor and test each wire to be the same resistance . if same it ok. Magnets harder to check would have to take apart.
also check the bearings for movement. only thing to throw a motor into unbalance is phase problem , damage to outer casing and magnets slipping.