Let's hope some of this information is helpful:
Causes of stuck in emergency mode:
No service (Can be caused by IMEI missing, generic IMEI, sim card not reading properly (usually the sim card reader physically damaged).
Solution for IMEI missing:
- Rewrite imei on phone, this is needed for generic IMEI (0049xxxxxxxxxxx)too (using tool such as Z3X box)
- Reflash firmware on phone (Using ODIN [Avoid losing data on just flash], Samsung Kies / Smart Switch [Will wipe user data on flash])
Sim card not being read:
- Re-align pins
- Resolder broken off pins
- Replace sim card slot.