Best Way To Handle A Voyager Wobble?

[Jase]

My question stems from the recent purchase of a 12C that is chronicled in this thread HP-12C+ (2022 version)
(I do not want to hijack the intent of that thread, so I'm creating anew.)

My new 12C has a wobble. The high point axis is NE diagonal to SW, and the wobble axis is NW diagonal to SE.

If I place three printer papers at either NW or SE corner, then all is firm again. (And I'm assuming I could place 1.5 printer papers at both NW and SE corner, and likewise be good.)

It could be that the rubber feet are the issue, or perhaps a slight twist in the frame - or perhaps a little of both.

What is the best way to handle this?
My thought is to simply lower the NE & SW high points by taking a very fine sandpaper to those rubber feet.

Anyone have a better idea?
I'd rather NOT "fix" the issue by putting clear tape and "building up" the low points. Too much of a hack for my taste.
But other than that, I'm open to ideas and would love to hear how others may have addressed wobbles in the past.

Thanks,
Jase.