VPI vacuum too much??

Ran a couple records with my new 16.5 yesterday. When I run the vacuum it overpowers the turntable and quits turning, unless I slightly push on the head of the tube holder. Is this normal when it's new?

Does the whole platter/motor stop turning, or does the record stay stationary while the platter beneath continues to turn?

Mine does the latter unless the clamp nut is tightened very securely. Check to may sure your clamp is tight whenever this happens. If your problem is the former, it sounds like your motor may have some problems.
Make sure the plastic screw on clamp is pretty tight against the record.

It may be the mat is spinning underneath the LP.
Make sure the arm tube is turned a tiny bit clockwise in the arm tube holder, so when your vacuuming the opening angled slightly towards the back. You want the fabric riding on the lp. This may or maynot be your problem just a guess.
make sure that the tube is turned all of the way forward or backward and not centered, the vac will stop the platter if centered. turn the tube till it stops on the pin.
I have had 2 units, I know your issue is resolved but my second one shipped with one of the platter screws loose, if it ever happens, remove the small cork center cover gently then pull platter and tighten........5 minutes back in business.
Stltrains, Jsa, and Chadnliz....Thanks for the extra tips...will file these away in case it occurs again and it's not the same issue....