Audio recording and loopback UL

I AM USING THE PCI CARD WITH WITH EM-12 chipset. When I make calls on 3G the recording of the clip in PCM WAVE 16 format feels good, while when I make calls VoLTE and record the audio clip I hear some holes in the voice. Is there any setting to do?

Thanks for your query in Quectel forums.
It is recommended that you first check the external CODEC chip or audio circuit according to the hardware manual, or upgrade to the latest version and then test to see if the problem recur,thanks.

I am using the pci card with em12. The audio should be that of the card’s codec.
Why then do calls recorded with AT + QAUDRD feel good on 3g and not on 4g?

i am also using em-12 with updated firmware