From your other post////////
Gnats......those are sewer flies that have invaded your black tank.......
Odor.......black tank is 'dirty'
With those 2 problems I have to ask
Are you leaving the black tank drain valve OPEN when connected to sewer hook up??
Because your 2 problems are common when you leave valve open.
With valve open..sewer flies come up hose and set up house in your tank
With valve open liquids drain out leaving poop behind....poop pyramid builds up, drys out, becomes hard and STINKS.
Always let black tank get at least 3/4 full before dumping. Needs the weight volume of liquids to carry the solids out.
Then close drain valve....flush tank (either with the built in tank flusher if you have one on side of rv, use a wand down thru toilet, hold toilet valve open allowing water to flow etc.) dump/flush-----a clear adapter on end of drain line between drain line and sewer hose lets you see when tank water is clear.
When done flushing/rinsing..close drain valve and flush couple full toilet bowls so bottom of black tank stays wet.
If you have stuff stuck in black tank.......add several gallons of water, dump couple bags of large chunk ice thru toilet..then drag trailer around on bumpy.curvy roads so ice scrubs the stuff. Then fill tank full and dump/flush.
Then drain grey tank..using it's soapy water to rinse drain line/sewer hose.
(I've never tried it/done it---but read about it here.)
If ice doesn't work UNIQUE makes a 'digester' that WILL loosen the hard stuck stuff
For the gnats......get some bug spray. Turn off water supply. OPEN toilet....and spray the whole can own into line/tank. Close toilet blade---turn water back on and put a little water back into bowl to provide vapor seal.
Leave it for several hours then flush toilet couple times. Repeat if necessary
Waste tank level indicators........junk. Little bit of stuff stuck on them.....they will indicate false level.
I haven't looked at my monitor in over 6 yrs.
Toilet 'burps' when you flush..time to dump
Sink/shower start to drain slower than usual....time to dump
On-board pump goes 'burrrrrrrrrr'...should have added water to fresh water tank cause it's now empty
Pedestal breaker tripping......that's because you are overloading the breaker (pulling more than 30A----A/C unit, microwave, converter/charger etc.) Place fridge and water heater on 'propane'