Multiple GCN notices being uploaded simultaneously, leading to multiple external events rather than properly appending to one

As in the title, multiple GCN notices of the same Fermi event (but multiple types, similarly to how we send preliminary, initial, etc.) were all uploaded simultaneously and led to multiple external events rather than appending to the same external event:

https://gracedb.ligo.org/search/?query=External+1364684424.33+..+1364684426.33&query_type=E&results_format=S https://ligo-caltech.sentry.io/issues/4059791894/?project=1425216&query=is%3Aunresolved&referrer=issue-stream&statsPeriod=14d&stream_index=18

There is not clear solution at the moment, other than making the exttrig worker concurrent, which will involve moving the rest of the work off to other workers. The main issue is likely from GCN.