After the evacuation of input chamber, I aligned the input oplev by tweaking the steering mirror just after the oplev laser source.

Then I measured the input oplev spectra as shown in the attached figure. The input pitch and yaw oplev spectra look very similar now.

I checked the oplev beam height at the injection, readout viewports. The oplev beam height at the injection, readout viewports were 110mm, 106mm, respectively. I tweaked the injection steering mirror and made the both beam height 110mm, but the pitch and yaw oplev spectra still look very similar.