RV plumbing - clogged drain?

My 2004 23’ forest river rv is my first fully paid for home. I know nothing about anything. I was using the sink/ drain tanks sparingly as i must use a toilet service for dumping. My kitchen sink began backing up, often slow draining to the level of the sink drain. I emptied the p trap and used chemicals, hot water, which ran through. I used the sink, backed up again, slow drains to the sink trap level. So i think… what if the rv is leaning that direction, could it be just not draining the sink bc of that?

Or, the pipes under the sink going from the p trap to the drain may be miss leveled, pointing downward toward the p trap so its not clogged, just again, the pipe itself not level or tilting away from the drain?

Anything else i should check?

This is a very unpleasant situation. A clog in the kitchen sink is often caused by an abundance of frozen grease in the pipes. This is a very unpleasant situation. A clog in the kitchen sink is often caused by an abundance of frozen grease in the pipes. In this case, ordinary salt can eliminate the problem. Simply dissolve 10 grams of salt in warm water and pour it down the drain. After five minutes, try using a plunger. Very simple and effective. I know how to fix everything in my house and even do repairs myself. Recently decided to decorate my house with beamed shelves https://www.scrooz.com.au/hardware/joist-hangers/. I recommend it to anyone who wants to furnish their rooms beautifully and comfortably.

Thanks for your suggestions. As it turns out, i had not drained my Grey tank bc it was not where i thought it would be. I was draining something right next to the black drain that is… something else. I had a port a jon company come to empty the black and they discovered the very full grey tank outlet, on the other side of the pullout. For only $40, i now have a solution to the tank emptying problem. My friends are fixing to tow Lucille into the barn for the winter. I plan to stay in it. Should be interesting! Oh, and i learned my tank sensors are basically useless.