I did a test with a custom OAuth2 connection that returned an incremented sequence number each time the user profile was requested and could not reproduce this situation. Checking the user profile through the Dashboard showed the last sequence number generated and rules execution also had access to the updated information.
Have in mind that under certain situation the downstream identity provider (your custom OAuth2 connection) may not get called. For example, if the user previously authenticated and a client application performs a prompt=none request (aka silent authentication) then the response may be provided automatically by Auth0 due to an already existing session and the downstream IdP would not be called (hence no update in the profile).
Confirm if the above could explain the situation (which I don’t think it is assuming the webtask log you mention proves the IdP is getting called) or update the question with more information about how the authentication requests that don’t trigger a profile update are being performed.