Are you using any non branded cases or magnetic sealed cases or pouches? Could be a simple block of reception cause of cheap material or disturbance.. Don't know.. - Certainly it hasn't been a reported issue since the Chinese Leak days. Sounds really weird that you get do bad signal. :/
This has been a KANG'd up message delivered from my GT-7000.
No, no... my Galaxy Note is absolutely naked!
After this issue happened again today I decided to enable mobile data roaming just to be sure that this isn't a bug about my Galaxy Note switching the tower which is providing signal. I will discover if this will make any change in the next few days, but in fact when using Samsung Stock ROMs I was used to always let roaming options enabled, although I never go to roaming areas, and I never had any issues like this.
Maybe Claro Brasil is so shi... that is making some phones loses signal when switching between multiple towers, or maybe it's something related to the phone thinking, in a fraction of seconds, that I'm going to a roaming area and disable.
I really can't understand, but if this roaming enabling thing solves my issue on AOKP 40.1, I will let you all informed.