I can't help with the original question, but just thought I'd say that I downloaded and compiled from source Freepbx/Asterisk on Armbian running on an SDcard and have never had an issue with choppy audio.
My version is FreePBX 13.0.197.31 which is fairly old as its been running for a few years, but it is still under support. Im using an orange pi one with 512Mb memory, The PBX which has light use (3 extensions, one PSTN gateway, one IVR, 3 trunks) but does do other stuff as well.