Sub Sonics and woofer pumping

So I’m noticing that on the lead in grooves where there is no sound yet but the record is playing my woofer appears to “pump” exactly once on every revolution. Also the pumping is more pronounced at the beginning of the record vs the end. 
Could have to do with the edges of records being a bit more warped than closer to the hole, but that’s just a guess. 
Is this vertical movement of the arm to blame?  And if so what is the solution here?  I changed cart thinking it was related to compliance, but this cart pumps as much as the last cart, and the new Grado i. Using now is suggested by VPI. 

I could add some wt to the head shell. But when I did that Nagaoka it didn’t change anything.  But I still could try I suppose. 

I could try setting the TT on the ground but presents issues of its own. iC’s aren’t long enough. 
I can’t buy another cart, so that’s out. 

Last_lemming, are you saying this occurs with more than one record??
the lead in grooves seem to be the noisiest park of the record. If this is just one record you have either a warp or a low frequency pulse at one point on the record. No big deal. If it is happening with every record you have a much more serious problem with the bearing or platter. The Cartridge is doing what it is supposed to do. If you are worried about the tonearms resonance frequency get a test record and check where it is. Very easy to do. 

You have two systems.  Have you tried the turntable in the other system?  Same issue there?  If not, I think @slaw may have pointed out what the issue is - placement.

It happens with every record to one degree or another. On the quite passages (lead in groove, etc). That’s why I don’t think it’s a resonant thing. If there is no music how could resonance contribute that much to the pumping.  I suppose the lead in groove could have low freq vibration. 
I will try and do a thorough inspection of platter bearing and arm pivot point. 
You know i do use the 2nd pivot point modification- I wonder if that could be causing the issues?  That’s easy enough check, I’ll just disengage it. 

Given what you’ve said about the rumble being worst in the lead in groove it would be worthwhile to try a periphery ring. I use one and it is very beneficial in terms of vertical movement of the record.