I searched for a scattering body in the REFL path.
According to the result the REFL path on the AS table is innocent.
The idea of the search method is given as follows:
Assuming that PRM is interfering with some other optics, I have estimated the optical distance between PRM and an object that interferes with PRM.
The optical distance is estimated to be 9.5 +/- 0.5 m.
If we believe this number the object is most likely outside of the vacuum chambers.