Hi,
The map/marker events have subtle differences between mapping services.
A MarkerClick in Leaflet always triggers a MapClick/MapMouseMove event as well, while this might not be the case in Google Maps for example.
More information on this behavior in Leaflet can be found here:
In your example you are changing the marker coordinates in the MapMouseMove event handler. In Leaflet this positions the marker outside of the cursor location. This means the MarkerMouseUp won't be triggered.
Implementing custom marker drag/drop code can be tricky. We recommend using the OnMarkerDragEnd event instead. However, please note that this event is currently only available in the TTMSFNCGoogleMaps and TTMSFNCLeaflet components, not in the TTMSFNCMaps component, as it is not supported by all mapping services.