Sourcetree OFTEN can't connect SAML-based accounts

My Bitbucket account is now authenticated via SAML. When attempting to add the account in Sourcetree, Sourcetree OFTEN fails to detect the completion of successful auth flow, with the only option available to 'cancel'. Result: I can't add the account to Sourcetree.

Repro:

• Sourcetree 2.7.6 on macOS

1. open Sourcetree > preferences > Accounts
2. click Add...
3. host: Bitbucket; auth type: OAuth; username: "no account connected"

• click 'Connect Account'

1. a modal dialog/sheet opens titled "Please sign in to this account:"

• enter email, get redirected to my SAML provider (AzureAD), authenticate
• after successful authentication, the modal dialog presents the default web view (list of repos), with no means to complete the process (ref attached screen shot)
• with no other option, click Cancel

Note that this is not 100% reproducible, it was happening all morning (~6 attempts) but in the very last one where I was creating the above repro steps, it worked - the dialog closed and the account was added.