Doom seems not work correctly sometimes. It has 90% success rate but after tried many times it is not like 90% success rate. Like @sparky95 said , it had some glitch with number of char in the map.
I had leeching at Platoon Chronos and tried on them , sometimes it works but sometime it just can't. I have no idea what cause it , might try more times and update later .
@Kai here is the video I think there is some mob u just can't use doom on it but I still don't know why.