Wow this is the first time I've seen on here someone else that has an older BP, I rescued a female normal she is around 20-25 years old. She gets a lil cranky when I change her tub, yes tub she's not in anything quite as luxurious as yours. But mine on the other hand doesn't seem to like water in the least, I've had her 9 mos. and have only seen her drink water the first month I rescued her. Neither of them had any water source and they were all housed together in a wire framed cage on layers of poop and old sheds .

Even when she goes into shed I have to mist her to get a shed from her, they all seem to not know what the water is for. My other normal female from another rescue however will sit in her water for days on end even poop in it and still remain in the water. Even when I try to remove her from the water which has the poop in it she gets all puffy hissy because she wants to stay in it. She will do this sometimes whether she is going into shed or not. So snakes are just weird sometimes. Like you I checked for mites and nope!!! Nada!!! Just a freaky behavior I can't explain. I just kept an eye on her, and nothing ever came of it. Good luck with yours.