I figured out part of my problem. I always anchored with my thumb up by my temple, but when I get tired, I tend to press with my thumb hard thinking I am keeping my anchor solid, when infact, I am pushing my hand away from my face.
I had to go to the bale and relearn how to anchor with my thumb down at jaw line, which felt about as unnatural as wearing my pants backwards. But since doing that, my anchor seems to be more solid without string hand torque and I can hold more steady with a cleaner release.
dave