Hey Corey - very first thought - you were recently talking about getting a new UPS for the elevator - did you do that? UPS's are notoriously hell on powerlines (I had an APC cause a lot of issues for me too).
Next - I'm not sure what you're doing for upstart for configuration vs. for the elk - if you have two PIM's - where they're located, etc; but I had an issue where I could get adequate signal anywhere else, but when I plugged the PIM into the wiring closet, I lost signal on one phase of the house, despite multiple phase couplers. Turned out to be a noisy DirecTV transformer that also lived in that closet polluting that circuit.
You need to get into Upstart and do a communications test - from the same circuit where the Elk is hooked in - either with the same PIM or with another plugged into the same exact location - then see if you're getting noise, and what signal levels you're getting. So much as a 2 and you'll be fine most of the time - but it's nice to get at least a 7+.
If you're losing signal, first look for UPS's and anything new to the house in the last month - and start unplugging them then testing again.
It's a pain to do the isolation test... in fact when I was doing mine, no matter what I isolated I wasn't getting a change; I even swapped breakers across phases and only made things worse. It was after I gave up for the day and decided to clean up a few wires (and add another power strip which had audio grade filters in it, which effectively isolated the cause of my noise) that I fixed my problem without even realizing it. I went from not seeing my 2nd phase much to having 13's and up.
Last - what switches are you using? Gen I or II? Do you have a phase coupler (if so, which one)?
