The get overlapping actors output array only contains exactly half or the greater half of the overlapping actors. I began a new first person shooter project and was able to reproduce easily. Both target actor and Class filter actor are set to generate overlap events with collision preset - Overlap all.
In the example below, if 10 cubes are overlapping than 5 are destroyed. If 9 are overlapping then 5 are destroyed. If 8 then 4, and so on.
UE 4.20.3
