(Now the CCD image is captured as a movie and the screen capture is easier!)
Various spot positions on CM1 and CM2 were tried to test how the transmission is dependent on the spot positions. CM1 has a few bright spots while CM2 shows very dark scattering most of the case. Attachment 1 is the example images of one of the best alignment that realized the transmission of ~96%. FM1 and FM2 also showed bright spots. The replacement of the FM mirrors does not improve nor degrade the transmission significantly. The transmission is still sensitive to the spot positions on the alignment. This indicates that the loss is likely to be limited by CM1.
Attachment 2 shows the distribution of the (known) scattering spots on CM1. The bright spots are distributed every ~1mm on the spot height and the beam (with beam radius of .5mmm) can't find a place where there is no prominent spots.
We will be able to examine if the transmission can be improved or not by replacing this CM1 mirror.