The folks in this forum run into everything! We have seen UPB issues created by the Pentair Intelliflow variable speed pool pumps. They are pretty nasty in terms of polluting the powerline. One of our dealers in CA uses UPB in his pool installation and service business and runs into this. He has had good success applying a large capacitor (Digikey part # P9412-ND) across the hot terminals of the pump. I have not tried this myself as we don't run into many pools here in Colorado, but I have passed this tip onto a couple of other dealers of ours who tried it with good success.
Apparently, it does not completely remove the noise, but it attenuates it enough that Gen2 UPB devices work very well. You would want to get it close to the pump and as far away from a breaker box as possible, as this capacitor could attenuate valid UPB signals.
So, just a suggestion even though I can't vouch for it myself.