Y axis funky, X axis perfect

So, V-Core 3.1 w/ Toolhead 1.0 and Beacon. I have a lightened gantry and metal gantry mounts installed. I used to have FMMM and AliExpress "heavy duty" bearings installed too but I removed both in my troubleshooting. All motor mount and Toolhead parts are printed in ASA-GF. Belt length is literally identical down to the tooth. X-axis is basically perfect except for a little high frequency bleed over from the Y axis. Y-Axis has weird crazy bits that have persisted through the entire troubleshooting process. Belt tension graphs have basically an identical 2 peak curve, but then alot of noise in the same spot as the Y graph. So, I'm about to lose it, but I want to check on my logic: -Toolhead: Likely in good condition without a cracked printed piece. If there was a bad piece on the Toolhead, or a loose part, then I'd likely see more noise on the X axis. There could still be something in the Toolhead that only causes noise when the head travels on Y, but I think I should look elsewhere first, especially with everything solid. -Belts/motors/bearings: All have been replaced with no changes. -Frame noise: I think I'd likely see some more vibration on X axis if there was something that was resonating at a specific frequency. -Y rails/carriage: My next likely culprit. Head feels rock solid and has no observable pitch during moving, either visually or by feel. But if for some reason the bearings in the mgn12c cartridges were "noisy", I would see the printer having almost no issue on X travel, but on Y travel, an underlubed cartridge or cartridge with contamination could lead to some grindy y travel. Or maybe even just a poorly tightened t screw on one of the rails? Any other ideas? This noise cropped up during some squaring fixes to resolve it getting bonked a bit, and I haven't been able to get it to go away.