First of all: are you mac user? since on our modpack we already found out that a couple of mac users have that issue since today without doing anything.
Second: Could you add a crash report, so those who have more knowledge can check it? i'm curious if it spits out the same weird errors (which i can't define) like for our pixelmon gen. mod(pack)
Tbh i can't really help any further, but maybe someone else with some crash-report-analyzing-skills can help out here
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NastasiaMoon //Pixelmon Generations PokeNinjas Network