Thanks for the feedback, everyone. I've also seen this occur at the end of a flight, but it's proved a bit of a tricky one to track down with it not occurring every flight! We do have it logged on our internal track,ers and we are actively investigating it.
With regards to co-pilot callouts, the AFCAS MODE warning shouldn't have any effect on them. For reference, the triggers for all the announcements/callouts can be found here: https://support.justflight.com/en/support/solutions/articles/17000151473-pilot-callouts-and-cabin-announcements-explained
Mark - Just Flight