We’ve had our Winnebago since 2018 and spend the winters in Florida along with several trips in the summer and Fall.
Our Black tank is drained usually at the 3/4 mark or so and then a quick spray with the black tank flush, the water draining in the hose view is clear and the sensors have never given us a problem. Once a month or when we break camp we’ll fill the black tank after dumping it and give it a rinse.
The grey is another issue, we’ve tried all the internet wonder products along with calgon, dish washer soap, dawn, taken it on a romantic ride in the moonlight with scrubbing bubbles, nothing cleans the sensors off. It registers 3/4 all the time and after a long stay the full light is the norm.
The only time the lights worked was when the rig sat for a month or so without use. Lots of junk came out of the grey tank when is was drained. The sensors worked for a few weeks, then they registered full again. Obviously, the soap scum, etc is building on the walls of that tank, chemically getting it off eludes me.
We’ve learned to live with it, but I have thought of installing a flush kit on the grey tank.