[Q] 3G > 2G switching issue

Hi everyone, I searched for a solution for my problem for a very long time, but found nothing. HOX has many issues with gsm network or signal, but mine HOX has a very strange issue with network mode switching. For example, I'm on 3G now and I set the WCDMA prefered in *#*#4636#*#* menu. When 3G becomes unavailable, HOX tries to switch to 2G network. But instead of switching to 2G, I get "No Sim card" icon and after ~30 second network icon disappears. I have to reboot the phone to recover the network. I made some tests and found, that this is not the hardware fault. I tried to change the radio RIL to any available and there is no difference. For now I don't know what to do, what else can I do... I will really appreciate any suggestions.;)
I can record a video to get things more understandable.