yea so there's no official consensus on what exactly causes the crash
renaming everything to include no special characters is one of the main things, the first guy who did it named his trainer "name" as well as all his pokes "name"- it was actually only one poke he used which he made 99 just to sweep the league easier
i've done some tests myself:
-all lowercase letters in the name seems to work
-tapus will work, but UBs and type null don't (for redoing the league)
-my first run i did with 5 mons, 2nd with 6, so i don't know if that matters
-i also changed my clothes to default, but had hair+eyes different, and didn't change those and it still worked
some way or another passing through the league is possible, but you'll probably ahve to fire up plhex
