Dangerous noise when braking at low speed

Squeaking when braking and at low speeds

Hello dear forum,

in advance, I'm writing this post on my cell phone, so maybe formatted a bit stupid.

For some time (3 months +) I have had the problem that a squeaking noise can be heard from the rear right when braking. As a rule, this occurs relatively quickly after driving off with the first to third braking and then persists. It occurs with normal strong braking, stronger or weaker braking is mostly noiseless.

That wouldn't worry me further if it weren't for the fact that a regular squeaking occurs after braking, which is related to the rotation of the wheel. Up to about 30-40km / h it is very well perceptible (with the window open) and from the outside you can also hear it well (which can be very embarrassing). So ... the brake squeaks when driving. But it goes away again after a while, but is then usually back after braking again

The rear right brake disc does not get any warmer than its counterpart on the left. At least you don't feel any difference when you touch it, or your fingers get burned because one is hotter than the other. If I pull the handbrake on slightly to medium while driving, it also squeaks.

What could that be?

- Disc is less than 2 years old, but about 40,000 km old, maybe somehow worn or dirty?
- once had the wheel down, didn't see any apparent errors or irregularities, except that the disc grinds a bit when you turn it, but it doesn't get hot ... Nevertheless, the piston seems to be stiff somehow?
- Brake cleaner didn't bring anything, or not permanently
- in rain / wet the squeak is gone, or much quieter

Has anyone had anything like this before? Any idea?