Momentary buttons can be dangerous, and should never be relied upon. No matter how robust you've made the timing on the Scada side, there is always a chance due to some external reason that a release event doesn't arrive at the controller. The rate of your Tag Group may have made your issue more prevalent, but I seriously doubt that it was the root cause.
See this thread for the reasons why.
This is still the correct answer if a momentary button must be used.