Just guessing here...

Some of this strange behavior being reported could be due to RF noise interference from other devices on your panel. All of the digital stuff on our panels can and will emit lots of RF noise. The amount of noise in any particular radio band can vary by huge amounts depending upon clock frequency harmonics and nuances of how your gadgets are wired up and how close the offending emitter is located with respect to your PF antenna. The presence of a closeby RF noise source can potentially overwhelm the low level radio signal from another PowerFlarm unit that's a few kilometers away. In such an instance, your PF transmissions would be unaffected while your reception performance is diminished.

One way to investigate this is to turn stuff off and see if you can get back to decent range performance. If a particular offender is thus identified, then you can start thinking about how to deal with it (and that may not be easy). At the design level it's often possible to slightly shift the clock frequency of the device processor with a simple code change. At the wiring level, sometimes using ferrites and twisting wires together can make a big difference. Or the answer may be to get the PF antenna further away from the offender(s).

My remarks here are based on related industry experience; I have no actual experience of PF noise interference to base this on. My own PF is working pretty good.