Reduce your anti-skating force by a good bit and see if it still happens.
Overhang, I have exactly same problem!! And I am trying to isolate the cause. VTF is okay. Azimuth is okay. I did not think about 180 gr v/s regular 'thin' records. Come to think of it , in my case also it happens with heavier LPs. At first I thought, it is due distortion, or due to dirt and finally due to vibration. May be I will learn some thing too.
It is annoying as hell, perticularly after spending big bucks on the new set up!!
I think it's quite possibly one (or both) of two things:
1.) The back of the armtube is hitting (ever so slightly) the edge of the record -- more likely with thicker or warped records, and/or
2.) The sector arc of the tonearm lifter isn't true (level) and/or isn't dropping away enough.
Rega has a shim for lifting the tonearm assembly higher. This will help, but only if you put a shim of similar thickness between the cartridge and the headshell.
This is a problem endemic to tonearms with thick armtubes (like the SME for instance) when the cartridge is short (from stylus to top of cartridge). If your cartridge IS short from top to stylus, and if setting proper SRA puts the tonearm dead level or even very slightly down at the back (never recommended IMO), then you could run into this problem.
I could be wrong, but check out this possibility, at least before proceeding to look elsewhere.