Looks like a rear spring problem to me.
Weight transfer is good, hook must be good
as per 60ft times.
Looks like more weight needs to be shifted over
to the left rear as it looks like it about to lose traction.
Might clamp the left front leafs and see what happens.
Or maybe unclamp the right.
Could trade sides with the springs.
Cheaper to try first than Caltracs.
I don't see any indication of body twist.
I see unbalanced springs.