Decals not redering on multiple objects when spawned with blueprint

I want to spawn a decal at the crosshair and use it as an AoE targeting marker. Spawning and moving it with the mouse works just fine, however depending on the area I’m aiming at the decal either is full size (if the area is bigger than the decal) or the size of the area I’m aiming at.If I move my mouse at a wall the decal is only showing up as a small horizontal line.
Furthermore the decal is only rendered on the object the trace is pointing at, not at objects that are above that object and should receive the decal (such as a stair; see picture 1)

Here are some screenshots of the problem:

Here is the spawing code and the material I’m using for the decal:

Where’s the problem in my code?