"seam line" after post-processing 360 photos

Hi,
I’m having an issue when post-processing equirectangular 360 photos in Rawtherapee 5.8.

In the final result, I can see a slight seam line on the vertical edge of the image (as in the image), and it is more evident when viewing it in a spherical 360 environment.
At first, I thought it could be a problem of boundary conditions due to many color correction operations, so I tried to enlarge the raw image making it “continuous” (from the 360 perspective) and then crop it back to its original size once the post-processing ends, but it didn’t really work.

I have used the following groups of parameters:
-Exposition (mostly brightness, contrast and saturation);
-Tone curve 1 (luminance method);
-Shadows/highlights;
-Tone mapping;
-Sharpness (contrast threshold + blur radius);
-Local contrast.

I did suspect the issue could be related to local contrast parameters, but it has occurred even without using them.

Does anyone know what operation could have generated this line?