Dell OptiPlex 5090: 3.5 mm headphones work at boot, but reinsertion stays "unplugged" (Windows 11 25H2)

I am troubleshooting a reproducible front 3.5 mm headphone detection failure across eight Dell OptiPlex 5090 desktops. Similar symptoms occur on some other Dell desktops, but those have not been confirmed to share the same cause. The failures were reported during the week of October 19, 2026.

Reproduction on an affected OptiPlex 5090:

1. Connect known-working wired headphones to the front universal audio jack, then restart Windows.
2. Sign in locally and play audio. The Realtek Headphones endpoint becomes active and both channels work.
3. Unplug the headphones. Windows changes the endpoint to unplugged.
4. Reinsert the same headphones fully.

Expected: Windows detects insertion and makes the headphone output available.

Actual: The endpoint remains unplugged, no device-selection prompt appears, and sound plays through the computer speaker instead. Booting without headphones and inserting them after sign-in also fails.

Reference machine at the time of the detailed test:

• Dell OptiPlex 5090, Intel Core i5-11500, BIOS 1.45.0.
• Windows 11 25H2, build 26200.9711; KB5127648 installed October 14, 2026. This is timing information, not evidence that the update caused the issue.
• Realtek Audio 6.0.9780.1; hardware codec DEV_0256 (ALC256).
• Microsoft High Definition Audio Controller 10.0.26100.9711.
• Realtek Audio Universal Service component 1.0.818.0; Waves APO component 7.2.0.16933 on this machine. An earlier diagnostic from another affected machine listed Waves APO 7.2.0.2578, so the versions need comparison rather than assuming the fleet is identical.
• Dell Optimizer Core 4.2.4.0 on the reference machine. Audio and Audio Device Pop-Up were enabled during testing. Optimizer is reportedly absent on some other affected computers.
• Reboot Restore Enterprise 13.1 is installed; protection was reported disabled during testing. Persistence with protection enabled has not been tested.

Troubleshooting so far:

• Restarted Realtek Audio Universal Service: returned to Running/Automatic, but reinsertion still failed.
• Restarted the Realtek PnP device: returned to OK/no problem, but reinsertion still failed.
• Restarted Windows with headphones connected: audio worked in both ears until unplug/reinsert.
• Audio, Realtek and Waves services were running. No matching recent application errors were found in the logs inspected.
• An audio driver reinstall was reported afterward without improvement; the exact installer and resulting versions still need verification.

No update rollback or BIOS change has been tested. These are analog headphones, not USB. A separate missing Headphones entry alone would not prove failure; the key observation is the endpoint remaining unplugged after reinsertion. RDP redirected audio is not being used as proof that the physical jack works.

Has anyone seen this exact insertion-versus-removal behavior? What diagnostic trace would distinguish Realtek/Waves jack detection, Windows endpoint state, Dell companion software, and firmware? Is there a supported driver/companion-app combination or targeted fix worth testing on one machine? I can perform physical plug/unplug tests and compare an affected machine with a working one. No specific Windows or Dell update has been established as the cause.