Yeah, this is probably it now that I think about it. That means no more Marisa laser spam as well. See this post as a little... confirmation.
I just spent about 6 times replaying the stage and marisa lasered, doll spammed, and otherwise hit more than one. They all were fine, but the moment I tried to master spark them it froze.

So yeah, it seems Spellcards are BAD BAD BAD and just generally hitting them with Marisa laser spam or normal attack on two over lapping eachother is just risky. Hopefully they get this patched soon, because I did notice that my test runs involved me getting owned too. Anything higher than Normal, and I probably won't be able to pass it.
EDIT:
Now I had it crash during Youmu and YuYuko's third card when I nailed both of them with one Pathouli card. X_x
I'm getting paranoid of using cards on bosses period now.