After this post ran dry I opened a support ticket with MG. I was able to get in contact with them once a day due to work holding me up. After a month of support, we replaced the X rail and carriage pair and that solved the problem.
unsuccessful troubleshooting involved:
-piecemeal disassembly to find the root cause
-reinstalling the V3B hardware
-trying a new carriage, carefully installed.
-removing the nema 17 damper (god the noise was terrible!)
-tightening the x rail
-tightening the belt tension
I tested how much slop there was in the rail and carriage pair with a test indicator, the results are in this video:
https://youtu.be/DvA7GVDR7lU
the total + to - slop was 0.003 inches. With the new set, the slop is less than .001 inches.
props to David at MG's support, He stuck through to the end!