Noise from eletric motor with belt on
If it is only noticeable with axial (along the shaft) pressure, I would suspect a thrust bearing. A thrust bearing is what keeps the motor from moving forward and backward along its axis. These are often ball bearings, so a cracked ball or a broken retaining ring can cause noise like this. If the sheave in your video is not directly attached to the motor shaft, then it could also be something in the coupling.