Abilities not procing damage or aplying cc (mainly ults)

Recently I've been in countering issues with abilities not triggering right like Nidalee's call of the hunt leap. Or doing damage and applying cc like Sonas ult and Yasuos ult (on me today). It happens randomly and I can't really see a clear reason it happens, but I've watched my friend ult a whole team with Nunu and they took 0 damage. I ulted Darius and Annie in a bush by red buff as Sona, did no damage Annie danced but Daruis didn't. Idon't know if i'm the only one who notices this but it would be nice if some one could look into the matter cause it happens frequently. I don't think it's champion specific either.