Well if all her other moves work fine in game I wouldn't think that's an issue on your setup.
Is it perhaps an issue with the PSA itself? Does it work properly over Sheik's regular slot? I can't think of any setting you could tweak in the configs that would effect an attack like that so drastically. It could be a bug in the module.
I know I have the spiderman moveset in my build but I don't think I've used any other Sheik based characters. From what I can recall he works perfectly fine too.
Ok so I tested out the moveset in question over sheik
Juri han:
http://forums.kc-mm.com/Gallery/BrawlView.php?Number=31982Moveset worked perfectly fine, so I try using Spiderman's Brawl EX files for juri and My Grounded side special does 999% and my Air side special crashes the game. So I take a look at Spiderman's module and guess what? apparently spider man uses Marth's EX Module file so my guess is that Juri's Moveset is simply incompatible with Spiderman's module. So my next best guess is to try using the same method I used to make Bowser clones to create a Zelda+Sheik module for Juri and another random zelda psa.