It's hard to make a case by case determination on each and every machine, if there are those who note seizing, or the record slips, or another result of mal-adjustment of the vacuum tower assembly can be cracked vacuum tubes.
A few months back, Harry W himself described the vacuum tower adjustment on the VA forum which I mentioned earlier.
If the collar is too high upm on the vertical vacuum tube, it will then permit the entire wand to come down further than it needs to onto the record.
With the vacuum pressure to continue to draw the entire wand down past the actual height of the record, this cause excessive pressure upon the record and wand, can be a cause of cracking the wand at its junction, and can perhaps be causing too much friction between the wand, and record to cause siezing, or slippage.
Excessive pressure as well could possibly also cause premature wear of the velvet protective strips.
Thanks for the heads up about the new VPI Delrin Vacuum Wand, will have to research this some more. Mark