Say you have a 50x300x100 box brush, and you set the material to have a scale that’s 2.0 & 2.0 with two sides that are 90* rotated. Then you pan the material on one side to have a specific design facing outward.
If you then rescale the brush’s 50 unit side to be 100 units using the brush settings, it resets everything in the materials except the material assignment itself.
I know there is a similar issue right now that’s known when you edit brush settings and the brush loses its world rotational information. Maybe this is also related?