Default [Q] Call recording

Hello.

I have the SM-G900F model with kernel 3.4.0-1182732

I have installed CallRecorder app by Skvalex, versione 1.5.2 full.

It is working fine (set device as it was a Note 3). The only problem is when I am connected to my car's Bluetooth. In this case the recording is either silence or white noise or a sort of buzz.
This happens with other recorders I have tried (Sanity, Automatic Call Recorder...).

I guess that it comes down to the kernel. Isn't it?
With the same apps on my previous smartphone (Motorola XT910 with modded ROM kernel) I had no such issue.

Any advice to fix the BT recording on my S5?