Strange line on left side getting brighter and brighter each iteration of inpainting

[UnconnectedBedna]

Since the project is what it is, I see no reason to create an issue but rather ask here to see if anybody has experienced this/knows of a solution.
This is with all models.

When inpainting areas of an image (not involving the left side of the image, ie anywhere on the image) there is a white line slowly appearing and I have no idea why.
I always use sizes that are dividable by 32, in this case 1152x864, but they appear no matter resolution.
I measured them in this example and the line is 5px wide. If I use higher width resolution it become wider, for example 1536x864 (16:9) the line is 7px wide, so it seems to scale with the resolution.

If only inpainting one or two times, it is hardly noticeable, but after a while it is very obvious, and trying to get the AI to remove it with inpainting does not work, I have to use for example Krita to remove the line manually.

Does not matter if inpaint area is "whole picture" or "only masked", the line slowly becomes brighter and brighter with each iteration.

Example: (I just inpainted random areas of the image 9 times, never even close to the left side of the image):

Any ideas/advice?