I've got a fake Xiaomi Redmi Note which has in fact a MTK6572 SOC on Android 4.2.2.
The problem is with one of the SIMs I use: in slot no.1 (WCDMA; unfortunately slot no.2 is GSM only) one of the SIMs behaves odd - when I put the SIMs in, the battery and start the phone - 3G internet works, but if I turn mobile data off and then want to start it again it's not coming back.
However, if I change the SIMs between themselves - the other SIM works fine when toggling mobile data ON/OFF.
The only solution to make mobile data available from that certain SIM is to factory reset the phone or swap twice the SIMs!
I would appreciate any advice.