We face a problem with zabbix events which never ends to increase steps (so escalating endless) even though they are already ok.
I'm not sure, if there is a way for you to reproduce this, because it mostly happens when action got disabled and enabled again. After enabling the action the escalating starts and the "ok" isn't checked/recognized.
We already had this Problem in zabbix version 2.0.5.

Maybe the problem could already be fixed in newer versions. That would also be ok for us, if we knew which version we need.

Hopefully my text does make any sense. Its hard to describe it. The screenshots can help understand when action got disabled/enabed and to see the timesteps of things happens.
Default step duration for this action is 900 seconds.
Our fix to stop this is to acknoledge the event.