All

Spray with hose, quick brush off, onto the boot dryer. Embrace the patina.

Take my input with a grain of salt, but when I was looking into the best options for maximizing a shigura setup, I read that the 9100 levers and master cylinders lack the proper leverage to force a large, powerful caliper to clamp down adequately. They're made with XC racing in mind, so they lack the raw power one wants for a more heavy duty application.

I asked the SRAM rep about this, they recommended removing and reinstalling clocked 180 degrees opposite and seeing if that resolves the issue. I have spoken with SRAM tech support as well, they don't have a specific millimeter runout that triggers a warranty. Usually it only becomes an issue when combined with a derailleur that has sloppy pivots. 1mm is ok, when it gets to 2+ it is hard to get the shifting working, at least with GX AXS.

There are a few things I'd look at if I were in this situation. One, I'd remove the cassette and put a tiny bit of grease on the freehub splines (if you haven't already) to be sure it's sliding all the way on smoothly. Two, I'd drip a little bit of low-viscosity lube around the edge of the cassette's integrated lockring -- sometimes on SRAM cassettes, that piece can be stiff or slightly binding within the rest of the cassette, and a little bit of lubrication can help it turn independently like it's supposed to. And three, once you're confident...

There have been a few transmission cassettes with lateral runout. I had one that had shifting issues and it was warrantied by sram through my LBS.

How is Fox calculator? I'm a Fox fan but I've been recommended tftuned's calculator which worked really good for me. And no, I have no connection to the company what so ever.

Mondraker is cutting it pretty close if they ship a 2.8 coil with a 70mm travel shock. Get the 3.25 coil as recommended by Fox, it has no impact on bike geometry and you won't be risking locking the coil and destroying your shock (and consequently your body) during a bottom out event with a few extra turns of preload.