2017 Jayco Pinnacle Grey Water/Black draining issues

[CapeCodGuy]

I have been having an issue with my 2017 Jayco Pinnacle when draining the tanks! The black tank will eventually show empty but the two grey tanks never go down lower than 1/3!

I keep my two grey tanks open at all times! I am wondering if the sensors aren't working properly and I need to use a wand in the tank!

Thoughts please

[Grumpy]

Sensors are known to be very inaccurate.