A quick update from Redmond.
We have passed along the additional session ids that came in this week. Thanks for sharing. We have 2 fixes that will be rolling out in April. The first fix is for users that don't have an Exchange mailbox. We expect this to complete deployment next week. At that point we will start looking at telemetry to verify the fix is working.
The second fix for users that don't have access to the root site will start rolling out next week but will take multiple weeks to roll out to all data centers worldwide. We should start seeing positive results next week, but we will be closely watching the global roll out before we close this issue.
To be clear we aren't looking at 1 fix to address this. There have been multiple fixes deployed to this point and we can quantifiably see their impact in reliability already. Most of the issues reported by session ids this week are aligned to the known fixes coming. Once we deploy the next set of fixes, we will continue to look at any remaining issues and prioritize them accordingly.
Thanks again for your patience and helping us work through this!