After upgrading to OTRS 5, we have this annoying problem with escalations. Notifications for all escalations - response, update and solution, together with warnings (notify before) are all going out at once

I've double-checked time setting for the 3 escalations (10,120,1440 minutes) - queue based escalations. I've set the following events for notifications - EscalationResponseTimeStart, EscalationUpdateTimeStart, EscalationSolutionTimeStart respectively.
What could I be missing?? Any help will be much appreciated.