The only thing that I've ever had go afoul in nearly 270,000 cleaning cycles with the HW-16.5 is that the screws that hold the platter shaft to the motor arbor worked loose. If the other suggestions made here for things to check to solve the problem don't work, try checking this.
You would need to tip the machine on its side and remove the bottom panel to do so. If they are loose, be sure to orient the shaft straight and vertical before you tighten them. You may also want to put a drop of Loctite on each screw before you tighten them.
Happy listening.
Jim Pendleton
Osage Audio Products, LLC