Bug with EXO V2 reconnect
There is a bug with the way Exchange Online V2 (ExchangeOnlineManagement 1.0.1) reconnects. If I have an On-Prem connection, it disconnects my On-Prem connection and makes a 2nd EXO, leaving the Broken EXO behind.
The On-Prem uses prefix "OP" for its cmdlets. When EXO times out ("state: broken"), and if I try to run an on-prem command (Get-OPMailbox), EXO somehow gets involved and disconnects my (perfectly fine) on-prem connection, then makes a 2nd EXO instead of refreshing the one it had (see screenshot).
We do use MFA. I'm going back to PSSession and basic auth for O365 for now.