Dometic toilet sloshes water unto floor

Here's a test I would do on my way to the dealer. Turn off the water pump and drain the bowl and use no towel. Then drive a block or two and turn left and right. Now stop and see if there is water in the bowl. If so flush it down then drive on to the dealer. if no more water then there is something holding water in the top of the toilet. Ultimately it probably makes no difference as it's under warranty. But I like to try to figure out what's wrong before I get to the shop so I have an idea if they're trying to feed ma a line.

Curiosity question. Do you open a sink faucet to drain the pressure out of the lines after you turn off the water pump?