Hi,
This is expected behavior - if the parameter value is such that no instrument is being played when you start the event, and there’s no other content that will play in the future (i.e. on the timeline), then the event is considered to be at its natural end and will stop. If you do want the event to continue to play even when the natural end has been reached, you can set the event to be Persistent using the toggle in the “Event Macros” area in the bottom right hand corner of the Event Editor.