Very common in the industry to have one monitor panel for multiple units. Panel may show 2 blacks and 2 grays with only 1 of each. May show 2 slides with only 1 etc.
If the “phantom” tank reads full all the time, the factory did something wrong.
2012 Copper Canyon 273FWRET being towed by a 1994 Ford F350 CC,LB,Dually diesel.
Airlift 5000 bags, Prodigy brake control, 5 gauges on the pillar.Used to tow a '97 Jayco 323RKS.
Now an RVIA registered tech. Retired from Law enforcement in 2008 after 25+ yrs.