After the CPB installation and yesterday's SUS/SEI tweaks I set my equipment back up and took another look at ITMx.
The yaw error is only approximate, ±150 µrad or so. Due to this large yaw error I wasn't able to get an accurate yaw measurement or a pitch measurement; getting a return beam back into the autocollimator resulted in the beam being steered off the optic. After talking with Hugh this morning the HEPI dial indicators did not show a large yaw movement, and double checking my setup did not yield different results. It is possible yesterday's SUS move induced the yaw error; it wouldn't take much more than pushing one side of the suspension 0.5 mm farther than the other to cause it. Will discuss path forward with Betsy and Hugh tomorrow.