I do think it is related to the pump (I don’t think they have the receiving antenna power set high enough), but that being said I had largely the same problems with the G5 stand alone receiver.
I finally installed XDrip+ on my phone and have been using it. I can confirm it to be an issue with the pump, or Dexcom receiver since I had issues with it too (just not as much). I wonder if it is possible for them to boost the Bluetooth receiving signal ability somehow in software. The other day I lost signal for more than an hour and a half with the pump within inches of the transmitter.