[LG v20 h990n] Calling does not work most of the time

Summary

When initiating a call, the calling app hang after 15 secs and close the call

Steps to reproduce Call the voicemail or any contact without airplane mode enabled

What is the current behavior? Very rarely it works depending maybe on the cell tower or the APN option or carrier mode hspda or wcdma ...

Don't know exactly what is causing that, maybe the modem firmware embbeded (nougat lg stock) is not working correctly with the android Q RIL layer?

What is the expected correct behavior?

Make call work :)

Relevant logs (adb logcat)

Don't have any

Relevant screenshots Not error shown, the call just stop by itself and go back to the dialer screen

Workaround Go back to stock LG nougat firmware :(

Possible fixes I tried LineageOS 17.1 for h990 and also LOS 18.1 but I end up with same issue

Inject a working modem from another recent LG ROM using the same CPU ?(call driver seems driven by the CPU)

Tweak LOS 17.1 or /e/ Q ril ?