Okay, after several tests tonight, I was unable to replicate this problem more than once... and even then it was less than one degree offset to starboard. (0.66 degrees) I am unable to determine whether the problem is related to stock SH3 or to the bearing overlay itself. The problem is not unique to GWX.
I have seen occasional references to this issue over the last couple of years, and the first references to this issue ocurred prior to the implementation of Pato's bearing overlay by GWX.
Considering that it appears to be an intermittant problem... I don't know what we can do to fix it.
It is not certain to me that replacing, re-working, or removing the bearing overlay will solve the problem.