I have had very similar issues.
When I hit the mic button within a chat (more prevalent in project chats) my voice memo will record (I can see the sound wave when doing this on browser) but when I hit the tick button to send the memo, all buttons disappear and nothing happens. Not sure what happens to my voice. Once it happens the first time, it happens all over the chats.
This is more or less a deal-breaker for me in terms of subscription. I will wait a week or two and then remove subscription if this feature is not available once more as it removes the most crucially useful part of the interface for me.