inconsistent WiFi Speeds

As I described in another thread, my wifi tests ran through iPerf running on a hardwired computer, to eliminate internet speed as a variable.  While speeds were fine when the client device was connected to the main Orbi unit, speed fluctuated drastically when connected through the satellite, even under very favorable conditions (client in the same room as the satellite, with no obstructions).

Exchanged it, but the replacement unit did the same thing.  Finally gave up yesterday and returned it, reluctantly.