I suspect its sucking air in from somewhere.
The transducers come off a T piece and then go up to the sensor so any air goes up and has no way to escape and compressibility gives false readings.
An engineer will just put the fuel pump on and slacken off the transducer couple until fuel comes out and that's the air gone and then tighten it up.
If it clears for a week or two then starts again you have air getting in somewhere.
Hopefully a spanner will come along soon and confirm or deny my theory.