Fuel gauge reading incorrectly

I also have used spectra with 0 issues.
Question to OP:
Have you ohm checked the unit to ground (when installed) to make sure you don’t have a grounding issue?
Resistance will cause the reading to go weird. A buddy of mine had the same issue. He painted his tank straps and has put a rubber pad on top of the tank. And, no ground strap crossing the sender to the fuel line. His readings were all over the place.
Syleng1