Problem with sculpting

[Tycho]

Hello guys,
So I'm new to sculpting in Blender and just experienced a weird problem.
As you can see on the provided picture:
https://imgur.com/a/l7Mz2KU
every time I try to sculpt at the middle of the plane, it also sculpts the same shape at the right edge of it by itself.
I've got an array modifier added to create a long pathway.
What I'd like to sculpt it into is a cliff alongside a road, but the raised edge makes the two array planes not connect properly and leaves a gaping hole between them as you can see on the second picture.

Any help is highly appreciated.

Edit: Another problem I just noticed: The shading is off for two road planes (look at the third picture) Any way to fix that too?

[Tycho]

I might've come with the solution for the first problem, haha. By applying the array first, then sculpting!
The second problem, however, still persists.

[still__alive]

Originally posted by Tycho:

I might've come with the solution for the first problem, haha. By applying the array first, then sculpting!
The second problem, however, still persists.

For the shading on the roads; check the normals and maybe flip or recalculate them if needed. If it is not that, maybe check to see if the problem roads are using different shading (flat/smooth) compared to the roads that are correct.

[The Renderer]

From the screenshot it looks a little like the road parts maybe don't actually have different shading but are simply angled slightly differently, leading to the change in reflection. If that's the case make sure you turn on smooth shading to prevent these hard edges. Else what still_alive said should help.