Problem integrating inpainting via an API on my site

[RROFFI]

Hello everyone,
I am looking to intreoduire stable diffusion inpainting via API on my site. I'm having a few problems. The area where the diffusion process should take place doesn't correspond to the given prompt and is too dark. When I did a different test, I realized that a black band surrounds this zone, which should cause problems later on. I can broadcast my code if you like? Do you have any idea where this might be coming from?
Another strange thing, when the part to be unpainted is on a large area covering 1/3 of the image and covering 3 edges, it works fine...
Here, I alpha-mapped the area in the center of the image and my prompt was "A boat on a lake"...

but when i brush a large part of it and when my brush goes as far as the corner of the image like this:

results are verry good:

Here a piece of the code :