Probably something regarding LTE (Which is not FRAND, so stop saying it is).
To my understanding, every smartphone vendor pays Samsung a fee for using LTE. Apple is the only one who doesn't.
Honestly, Apple needs to stop stealing Samsung's technology. Designing a rectangle with rounded corners is something a 2-year-old can do.
Making critical innovations in LTE, however, is well worth patenting and protecting. Apple is really a hypocrite. They claim that someone else making an electronic device in the form of a rectangle which took 0 ingenuity and $0 in R&D cost is considered copying and a threat to innovation everywhere, but when Samsung spends a shitton developing critical LTE technology, they think freeriding on Samsung's tech when everyone else is paying isn't a threat to innovation.
If Samsung gets the idea that people are allowed to steal their technology and not pay a fine, why would Samsung spend billions in R&D? What Apple is doing is a true threat to innovation.