Some things to clarify, just in case it is in fact "behaving as intended", as SE frequently replies:

did you do any damage to initially seat hate on it? In particular, any action that isn't just a quick volatile hate spike that fades quickly...rather something that has slower decay.

Are you absolutley sure it didn't do something to cause hate loss--something like Mayhem Lantern or Deathgnash are two examples that can cause instant loss of hate.

In other words...did you just pop and run, or did someone play with it for a few seconds and then run. If the latter, did it have enough time to fire off a move and you just didn't see it in chat?