how to prevent decal overlap

Dear experts,

What I would like to realize is that upon bullet hitting the wall, a new decal is created, and if it overlaps the old one, the old one will be destroyed.

But I notice that after bullets hit the wall, the number of overlapping actors of the wall is always 0. Also the number of overlapping actors of the new decal is always 0, even though it is successfully displayed on the wall and it overlaps the old one for sure. So did I miss any important property of decal? How to detect decal overlap?

Thanks a lot.

After some testing, I found that to enable overlap detection, the decal actor shall not be used alone, instead it needs to be placed into a regular actor class as its component.