There’s a problem with my landscape, for one of the landscape proxies (because I use world partition). the shading of the proxy is lighter than the others
And you should make all “proxy" materials the same base material you create custom with the specific textures for the landacape as part of the instance definition. Only way you can be sure the values match is to specifically not allow them as an option.
Also, and more appropriately, you should only be using the proxies and not the landscape at all.
I’m assuming you are baking landscape impostors - maybe that isn’t what you are doing, but it is what you should be doing which can be normally considered a “proxy".
Each of these baked impostors have their own material assigned that contains the texture captured when you generated the impostor. Usually they also have a specular value that isn’t set, and a different material shader space than landscape materials. The combination is what ends up driving the difference in lightness/shade.
If you aren’t baking landscape impostors, you should look into how that used to work (because no idea what the deal would be with newer engines that don’t work anyway) and not use landacapes into final builds…