Default [I9001] signal loss

Hi, i've a problem with my i9001; suddenly my device don't receive the signal properly and allow me to do only emergency calls. After i activate/deactivate airplane mode few times the device receive the signal; signal drops are random during the day. I've tried to reflash and change the baseband with odin but nothing change; i've tried different roms (stockgb,cm10.1,cm11) but it's the same. The device has not fallen down or anything like that. Actually my baseband is bukp7. Please give me some advices.