Maven not collecting map bosses

bug ref 3,473,197,084

I finally got a map drop with "Occupied by the Purifier" to complete my maven collection thingy and fight them all.

I fought the guy and killed him but maybe too quickly because the maven never collected the guy, even though she was present and buffing the guy and everything!! Really freaking annoying.

This is not the first time this has happened, it also happened in one of
the synthesis maps as well, which are very hard to find without trading stupid amounts of currency for them.

Please fix, or explain how this is by design so I can avoid it in future, thanks :)