If the next one does the same thing, could you omit the power conditioner?
Searching the reviews here:
Someone said they connected theirs to an oscilloscope, and it was a clean sine wave output, like utility power. If that's the case, the power conditioner may not be doing a lot for you?
It depends on what the conditioner is trying to do, I guess. If it's trying to smooth out the sine wave, then that shouldn't really be needed. If it attempts to help "fill-in" brief voltage sags, it might be able to provide some benefit. But brief voltage sags due to sudden big loads (such as a compressor starting, which sounds like it wouldn't apply here), can be indicated by listening for the engine suddenly slowing down as a big load hits. And that can be minimized by leaving the engine running full-speed, rather than setting it to reduce the engine speed as the load reduces.
But I'm not an EE, and I have always been a bit puzzled by power conditioners, and what exactly they're supposed to help with. Maybe they're really effective, I don't know. I better understand how an expensive "online" UPS is able to clean up power, as it can use the input power, and its internal batteries, to sort of re-create the sine wave that is needed.