I plan to do a writeup with some more photos once (if) I manage to fix this receiver. The odd part about this problem is that the loss measurements are consistently too high, and they don't seem to be affected by whatever is connected to the source port. Today, I had a 10db attenuator connected, so I'd expect around 20db of return loss, but the measurements hit -10db!
The generator definitely seems to be working though, when set to a frequency sweep for 1.5 GHz to 1.5001 GHz return loss measurements, I see the correct signal at the coupled port. I also see some weird reflections at the transmitted port, I'm not sure if this is normal? But I don't think the problem is with any of the switches, because I see the signal all the way back on the analyzer input path (although the signal is radiating enough that I can see it without even probing the board), and because I'd expect the measurements to be super low if the switches failed, since there'd probably still be a bit of parasitic coupling? I'm wondering now if the rework performed on my unit might have something to do with this problem.