Fujinon B4 zoom drifting adjustment

Many years ago I had a problem with a Fujinon B4 zoom drifting without moving the rocker on the lens or the thumb demand unit.
I remember that there was a front adjustment pot on the lens to fix this but I can't remember which one it was.
Can anyone point me to the correct adjustment as my lens has about 8 different tweeks available.

Baz
I remember that there was a front adjustment pot on the lens to fix this but I can't remember which one it was.
Can anyone point me to the correct adjustment as my lens has about 8 different tweeks available.

Baz