If I recall correctly, I placed those beam dumps everywhere because the transmission table ghost beams had gotten out of control. Particularly bad was out of the cavity, it seems you have left those beam dumps there but I would double check their status. There was also reflection from the first lenses back into the cavity that I tried to have the post-cav beam dumps block, unclear how successful I was.
Also bad was reflection from the ND filter we had on our pre-RFPD lens, it seems like you have removed this lens which is great. Also, there was some backscatter from the third camera I had installed at the other end of the recombination BS that unites the North and South path light, seems like that is gone as well, you might dump that light if you aren't already.
Finally, the scatter from the IR cameras was like a diffraction grating pattern that went everywhere, it might be prudent to place those black glass beam dumps with the holes in front of them.
I reinstalled the beam splitter, steering mirror and PD in the transmission path. We have the beam profiling measurement and can reposition the detector more optimally in the near future. But for now we need to get back to the scatter hunt: specifically the 500 Hz feature that haunts the area directly around the north path pre-mode cleaner (PMC).
Some of the beam dumps were removed as they weren't bolted down or were in the way of the beam profiling (sorry Craig).
A few things to note: