Left axle, inner boot? That was my nemesis: I was tearing boots every weekend which got worse when I started doing the longer National/Majors races. Raxles claimed I was running the car too low (I wasn't), Gator thought I might be picking up road debris (with a full undertray?) That's when I moved my GoPro to under the car and saw it happening (see video above).

Brass tube under the smaller end of the inner boot resolved it completely. I believe Gator does this for all axles now.

GA