Units damage structures unintentionally?

So I was playing around with some of my code and I found something really interesting. Apparently, structures register a damage event every time an enemy unit comes within a certain range to them. Of course it's 0 damage but it can do some really weird things to triggers. Now maybe I'm in left field here because I haven't done a lot of extensive coding or anything serious in a while so I'm not sure if this has been reported (couldn't find it/didn't search with the right phrase) but the only thing that seems to trigger this is if the unit is considered a structure. Remove that tag and this doesn't happen anymore.

I'm late in noticing this, can anyone explain why or how this occurs? Otherwise this might prove useful info for someone... maybe.

Can you post a map with this "bug" being shown? I don't think I've ever had those problems.