If i understand correctly you're main event calls another event which takes you to the 1st map(training halls)...the issues,
i believe:
that the main event must resolve with it directly teleporting you to a map, you cannot call another event that indireclty takes you to another map, nor can you branch off into/events executing simultaneously as you do during normal play.
the Main event may set up infinite variables, assign the player infinite items...however you must go directly to a map at the end.
start game-
teleport 'arbitrary_screen.loc' //in fact you oculd just make this a black screen also.
wait X ms
engine call: new game
newgame-
...// blah blah blah, automaatically proceeds to 'main.cet' when it ends
main.cet-
//bare bones
map position
teleport 'checker'
checker would have a local initialization event, which would then do the conditional to test on where to take the player next
this by all means should work.
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... bwahhaaaaahaaaaaugh fooooolish sammurai.