Yeah, I flashed stock firmware and performed a factory reset, it was clean. Then I proceed to root, install FreeGee, BusyBox and then CWM 188.8.131.52 and then flashed the CM11 M5 ROM, has been stable for a while, then it crashed. This is the report:
"DemiGod Crash Handler : Subsystem Crash! : External_modem (Undefined error)"
BTW, I performed a backup of EFS partition 3 img files with FreeGee.
I had to flash stock firmware once more due to crashing, it's completely unstable with CM11 M5, I'll flash CM11 M4 which was perfectly fine and see if it becomes stable.
EDIT: still crashing with CM11 M4, the latest CM ROM really screwed my phone.
EDIT 2: sent my phone to local repair service and the main board was replaced, with a new IMEI. It seems there was indeed a hardware issue. I had a SIM card which I had it adapted into microSIM format but it wasn't recognized by my OG. After the motherboard replacement, it's being recognized now. I have backed up EFS partitions and modem packages following the tutorials on Q&A. But I'm enjoying stock ROM, it has some nice features which I didn't find in CM11, I'll stick with it for a while. I don't believe there will be any more issues regarding CM11 though.