i have a latest version of pvpmanager download from here: http://ci.md-5.net/job/PvPManager/
and i found a bug with feature "kill when player combat logout".
as you can see in this video: https://vimeo.com/164833537
(my network has error, so i cant upload to youtube)

I think minecraft or spigot fixed this bug, doesn't happen anymore to me.

This is only on premium version right?

both free version and premium,

So, like i said in the discussion thread. Not sure if this is a minecraft or spigot bug yet, i verified it does happen with other pvp log plugins though.
To make it happen it simply takes killing a player right before he logs out.