That's why I build in a "logging system" =>
http://www.papy-team.fr/roster/index.ph ... :302&log=1 to see who is uploading.
If 'something' happens with the lua generation, or even the uploading goes wrong, I know who to contact, or even exclude that officer from uploading.
About the GEM Calendar addon, I still use the same approach: when the upload is acceptable (player Title [0,1,2, etc - 0 = GM] and the player has all the needed canals (GEM is multi channel) the I accept the upload.
Before taking in the events, the table are all purged.
There is no such thing as an intelligent merge
If needed, take a look at my code to see how the logging is done.