Android File Transfer and Multi-user macOS

 I had some issue with Android File Transfer, which was related to specifically Galaxy S21.  Later a similar issue - symptom wise anyway ("could not connect to device") - developed, but sporadically happened to all sorts of devices, from tablets to Oculus.  Eventually I figured it out, and purely by luck and intuition, that it was due to multiple user (interactive UI) sessions ongoing at the same time.  My theory is that upon connection, the app sends whatever signal to the UI/logged in user, it'd get multiple responses back, which confused the app and led it to refuse the connection.  It's very much a personal app I guess...