Yes, tried multiple SIM cards. None work on a custom ROM now. My first flash with SlimKat 8.9, was golden in every way but the camera. Then nothing but trouble with everything else. Even the "stable" CM 10 wasn't stable for me. I just managed to get a pure LG 20d ROM installed, and everything works fine. Battery life is even great. I started flashing custom ROMs to get a better device, but now with a rooted, Xposed, and stable stock ROM, I kind of wonder if it's worth bothering. It would be nice to have KK, but I don't really miss it TBH. I still have root, I still have "most" of what I liked about KK, and there are no more bugs.
Same with my original Nexus 7. Both had been flashed to KK of one sort or another (MANY times before I gave up), and both developed issues from it no matter how I did it. Went back to stock JB on both devices, and everything is fine.
If I flash any more custom ROMs I'm def going to keep a solid JB backup ready to get a stable device back if need be, and so far need be indeed.