So this is not a new phenomenon there is this thread from a year ago:
It is a long thread with no solutions beyond what is known here, namely that disabling all but one codec on certain phones will fix the audio.
It appears from this thread, that not all versions of Asterisk have this issue, unless there is another explanation to why working systems suddenly started having this issue after an update. I had understood this to be a phone issue, not an Asterisk issue. There is a brand new Asterisk ticket (watch it for updates) discussing this here:
https://issues.asterisk.org/jira/browse/ASTERISK-26423