We're using FSv10.5 on Debian 10 with verto/Opus (i.e. no codec explicitly configured), and we're using a conference. We've tried these settings but they're having no effect on the recorded mp4s:

<action application="set" data="RECORD_STEREO=true"/>
<action application="set" data="record_sample_rate=44100"/>

Instead:

1) The mp4s have the same audio in both channels, contrary to https://freeswitch.org/confluence/display/FREESWITCH/RECORD_STEREO

2) The sampling rate is 8kHz, contrary to https://freeswitch.org/confluence/display/FREESWITCH/record_sample_rate

FWIW:

a) We noticed that mp4s from a year ago when we were using FS 1.8 also have the same audio on both channels.

b) We also have this, and I don't recall why and can't find a description in confluence:
<action application="set" data="record_concat_video=true"/>

Is it that these are known not to work with conferences, or is there some setting we might have overlooked?