Lumia 1520 SIM card dropping

[northstl]

I recently been experiencing signal loss of SIM card. I replaced SIM card and it continues to happen from time to time. Really a the worst times. I've reset phone multiple times. Problem still exist. How can I rectify this problem?

 

[Aravind Belagaje]

Are you using a dual sim phone? Is the problem like mobile shows good network at the status bar(above the screen) and unable to make or receive calls and if you try to activate flight mode the mobile freezes.

That problem was there with my Lumia 630 ds the only solution we got is using a single sim it was a firmware bug and not fixed by Microsoft or Nokia.

Have you used windows recovery tool? Because most of the times problem like this happens because of firmware issue which will not reset by hard reset and you should go with recovery tool.
Note: Backup you stuff before using the recovery tool and the reset will give you windows 8.1 which than can be updated to windows 10 using update advisor app on store.