> Hmm, do you know on what occasions this happens?
> For what triggers is side = "none" used?

Well I haven't tested it all, but I had to edit these two triggers:

NAME,CAUSE,EVENT,COUNT,SIDE,TEAM,LOOP
air1,destroyed,airstrike,0,none,none,1
hunt,destroyed,all to hunt,0,none,none,1

Most of the single player maps from the original general.mix cannot be saved because they use a lot of triggers where side="none", so maybe those maps are a good source of information.