Do Oral Discussions have to be recorded (audio, video, transcript)?

Oral discussions?   Do you mean oral (proposal) presentations?

Discussions need to be memorialized and any outcome that affects the interests of other bidders needs to be promulgated equally in writing, so video and audio recording are not really viable (i.e., you wouldn't ever release a verbatim record of 'discussions' as defined in Part 15).  Oral proposal presentations are memorialized by the presenter providing hard copies of the presentation.

So the answer is that audio/video/transcripts aren't really useful or viable in either scenario; just take good notes and publicize any resulting Q&A related to the RFP.

I mean oral discussions, not oral proposal presentations.

No they don’t.  It’s always a good idea though to summarize issues in writing.  This is especially true when the offeror is supposed to respond with proposal revisions.