@TK-422 - Chris, Your thoughts do give me one more option. It’s possible the entire center column that houses the z-axis elements and router could be rocking left/right. That would indicate loose v-wheel as @DanoInTx just mentioned. I’ll check them.
The aluminum block holding the router - I just reset and leveled it to my spoilboard before running my last test that you see above. Hopefully that’s not the issue. z-belt seems nice at tight, “guitar string tight” as Will said. Maybe there is a screw or fastener I’m missing?
Either way, I still wonder how all this accounts for the router cutting down past the bottom of my stock on one side, then leaving slightly more than onion skin on the other… of every separate object. I had another thought - most every uncut portion starts after a tab. I use 3D tabs. Anyone have reason to believe this is the cause? I’ll remove to test but thought I’d ask. Thanks!!