I have a rack of mixed Sennheiser receivers that I just put together this year and am still trying to fine-tune. Generally speaking we have a pretty quiet RF environment in our location, along with a thick-walled institutional building that helps block outside signals, but I'm suddenly having trouble finding free frequencies. I realize that RF environments change quickly, but I'm seeing behavior that I don't understand. Normally I hook everything up and scan with one receiver, then use the "list" from that receiver to populate the frequencies on the rest. In the last few days, I've been getting a lot fewer free frequencies than before when I scan (7 at most instead of more than 20) and scanning with different receivers on the same band yields widely different amounts of free frequencies (scanning with an EW300 gives 7 free at most, scanning with an EW100 gives me multiple groups of 12 free). I haven't yet tried pulling individual receivers out of the rack to test them independently, but that'll be the next step after a small event tomorrow for which I need at least 8 functional channels. My rack is split into two sections so I can mix and match for different size events- Section 1 is a 4-pack of EW300 G3 A band receivers, all powered and distro'd by an RFVenue Distro4. Section 2 is 3 EW300 G3 A band receivers, 6 EW100 G2 A band receivers, and 3 EW100 G3 receivers, one each in A, G, and B-bands. There are 3 RFVenue Distro4s in this rack, powering and providing antenna distro for these 12 receivers, and I can cascade out of the 3rd Distro4 to the other section's antenna input to tie them all together. Everything is used with a pair of Audio Technica ATW-49 antennas connected with 50' 50 ohm coax cables. I realize that it's a bunch of disparate gear kludged together, mostly because of budget constraints, but it's all functioned pretty well for the better part of a year. Is there anything I'm overlooking that might be causing this weird behavior? Thanks for any help!