u/ArchonTheta

Posting this to see if anyone else is hitting this across their fleet.

After KB5083769 installed on a handful of Windows 11 25H2 machines across multiple client sites, we started seeing the following across 6 of our 100+ managed endpoints:

• Outlook Classic (possibly new outlook as well) stops delivering new email to the inbox entirely across all configured accounts, no error displayed, closing and reopening Outlook temporarily resolves it, but it keeps recurring
• NinjaOne Backup file/folder jobs failing silently was another issue we noticed on these affected endpoints.
• DISM failing with networking errors mainly with:

​

Error: 0x800f0915
The repair content could not be found anywhere.
Check the internet connectivity or use the "Source" option to specify the location of the files that are required to restore the image. For more information on specifying a source location, see https://go.microsoft.com/fwlink/?LinkId=243077.
The DISM log file can be found at C:\WINDOWS\Logs\DISM\dism.log

• Network Discovery broken - sits spinning within File Explorer under Network.

All machines run the same stack (NinjaOne, Huntress, Emsisoft, AutoElevate, M365) and received the patch at the same time via NinjaOne. Different client networks, different hardware, no single common thread we could isolate other than the update itself.

Our best guess at the root cause is the SMB compression over QUIC changes in this patch. The regression appears to cause persistent connections to silently stall after the initial handshake with no visible error, which would explain why all four completely unrelated services were affected simultaneously across different networks.

Uninstalling KB5083769 and rebooting fully resolved every symptom on every machine we tested. One machine is past the 10-day rollback window so that one is stuck waiting on Microsoft.

There is at least one other report on Microsoft Q&A describing the same thing: https://learn.microsoft.com/en-us/answers/questions/5865394 and OP has also posted in r/Outlook about this too.

Has anyone else seen this? Curious whether others have found a workaround short of uninstalling the patch. I still have 1 machine with the problem and the only thing I can think of is a Windows reinstall keeping files/settings. But this machine is always in production so getting this from the customer is going to be problematic.

Posting this to see if anyone else is hitting this across their fleet.

After KB5083769 installed on a handful of Windows 11 25H2 machines across multiple client sites, we started seeing the following across 6 of our 100+ managed endpoints:

• Outlook Classic (possibly new outlook as well) stops delivering new email to the inbox entirely across all configured accounts, no error displayed, closing and reopening Outlook temporarily resolves it, but it keeps recurring
• NinjaOne Backup file/folder jobs failing silently was another issue we noticed on these affected endpoints.
• DISM failing with networking errors mainly with:

​

Error: 0x800f0915
The repair content could not be found anywhere.
Check the internet connectivity or use the "Source" option to specify the location of the files that are required to restore the image. For more information on specifying a source location, see https://go.microsoft.com/fwlink/?LinkId=243077.
The DISM log file can be found at C:\WINDOWS\Logs\DISM\dism.log

• Network Discovery broken - sits spinning within File Explorer under Network.

All machines run the same stack (NinjaOne, Huntress, Emsisoft, AutoElevate, M365) and received the patch at the same time via NinjaOne. Different client networks, different hardware, no single common thread we could isolate other than the update itself.

Our best guess at the root cause is the SMB compression over QUIC changes in this patch. The regression appears to cause persistent connections to silently stall after the initial handshake with no visible error, which would explain why all four completely unrelated services were affected simultaneously across different networks.

Uninstalling KB5083769 and rebooting fully resolved every symptom on every machine we tested. One machine is past the 10-day rollback window so that one is stuck waiting on Microsoft.

There is at least one other report on Microsoft Q&A describing the same thing: https://learn.microsoft.com/en-us/answers/questions/5865394 and OP has also posted in r/Outlook about this too.

Has anyone else seen this? Curious whether others have found a workaround short of uninstalling the patch. I still have 1 machine with the problem and the only thing I can think of is a Windows reinstall keeping files/settings. But this machine is always in production so getting this from the customer is going to be problematic.