"Defective" is a relative term when dealing with the tank indication system.
The kitchen sink gets tons of grease and food particles and since the level indicators use resistance to determine liquid level, any electrical path from the probe to the ground probe will show as some level of "fullness."
The more "shorted" the probe is, the "fuller" the tank will indicate.
Even the 1/3 probe will indicate "full" is the resistance to the ground probe is low.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW