I can confirm this behaviour on my Xperia 10 II - Dual SIM / 4.4.0.64 / Fello Sweden.
Test 1:
- Sailfish phone connected to 4G, WiFi off.
- Make a call to Sailfish phone
- Reject call on Sailfish (phone will show 4G is disconnected, lasting for 10-30 s)
- Immediately call Sailfish phone again
- Call goes to voice mail
Test 2:
- Sailfish phone connected to 4G, WiFi on and connected.
- Make a call to Sailfish phone
- Reject call on Sailfish (phone will show 4G is connected)
- Immediately call Sailfish phone again
- Call goes trough to Sailfish phone