GC Events (randomly) removed from Edge 1040

I have a number of Events in Garmin Connect over the next 6 months or so.

I have pushed these to my Edge 1040 and seen them appear successfully in the on device Event list with the correct Primary Event set on the device

Then, seemingly randomly, one or more of these events will disappear when I power up my device. Not always the same one or two Events.

Can't seem to see any logic.

When I push the Events to the device again using GC they reappear again on the device, but then the same thing will happen again...