Xperia Z3 not recovering lost signal/data topic

I have this problem with my Z3. I commute to school by train and every now and then I lose signal because of tunnels etc. But the phone is having a hard time recovering signal. Sometimes I have to reboot. Sometimes theres the red X on the SIM icon but usally it's just that there's good signal strenght but no data connection. Other times a reboot doesn't solve it instantly and I'll just have to wait. Othertimes I have to go and manually select my carrier (Tele 2, Sweden) but it doesn't work all the time either. So there's no consistent fix. Anyone else experiencing the same problem?

I've got a D6603, rooted .77 (PRFCreator). The problem started occuring before rooting. Can't remember if it was before updating to .77. Carrier is Tele 2 in Sweden.