I don't usually go public with info prior to a design change being issued but will in this case because it is rather minor to describe.
The looseness is not because of heat on nylon lock nuts.
Yes, the brake disks do get hot but the disks are conductivity isolated quite a bit from the brake mount flanges. If it were a problem we would have seen serious issues by now with the airplanes that use bolts and nylon lock nuts to attach the axle to a flat gear leg.
The looseness is caused by the spacer bushings being made of 6061-T6 aluminum. It is just not a hard enough material to take the shaking / pounding of the wheel fairings. Over time the bushings suffer plastic deformation and reduce in length slightly. Once that happens, the bolts get loose and the wear process gets accelerated until the bolts are re-torqued.
A change is in the works to switch to steel bushings. The ones for the RV-10 will likely be all one piece in steel instead of the current steel reducer bushing and aluminum extension bushing.
Please don't call the office asking for the new parts. It will be a while until the change makes its way through the internal process. Once it has, they will then be available. In the mean time,it would be very simple for someone to substitute the same dimension steel tubing on a 6A, 7A, 8A, or 9A.