Bugged/stuck events
All those events has been reported for more than a year (several times).
Some work only a few hours after a server reset, other may work a little longer, some times, they may or may not get stuck at all and sometimes, event get bugged after a Living World update.
And no, there is no other solutions but wait until a server reset and rush before they get stuck again.
And don’t wait for a solution. Just, let it go.
-ArenaNet
Sometimes, the challenge in fixing a bug is not in knowing that it breaks but in knowing how it breaks. If you see one enter a stuck state while you are at it, please report it.
//Portable Corpse
Yes, yes. I see that we are supposed to beat up a nonexistent Malchor. But is that because Malchor never appeared, or he died while we were beating him, or because nobody told us to go find him? And then, from any of those causes… Why did they come to pass?