The default codec settings for audio aren’t always honored. It seems that If a video is imported without audio and interacted with in some way, the subsequent interactions with sources will set the audio codec to None.
This is when trying to paste a preset or settings onto multiple videos and sending to the export queue?
There was a previous issue where the frame rates were overwritten and all set to the first clip selected when exporting that the team resolved. I will send them a message to look into this to see if this is a regression from that previous issue.
EDIT
They are already working on a fix for this to have it ready for the next patch update, hopefully.