Nexus 5 signal drops immediately when making call My Nexus 5 running on Marshmallow and it has Last ota security update provided by Google at the time of end of support.

I’ve a perfectly working SIM card. Using this sim card to make calls from nexus 5, but before the call gets placed the mobile signal drops to zero.

When the call is disconnected the signal resumes back to normal.

I tried soft reset, hard reset and airplane mode on/off. But nothing works.

Any help would be appreciated.
Recently I have installed Lineage OS Android 8.1.0 (Oreo) custom ROM in Nexus 5.
It has resolved the issue and I'm able to make calls successfully now.
I believe there should be some issue in Android Connectivity Services application and it might have got resolved by the OS upgrade.