Integrated mode intermittently fails with "You must be running this command in PowerShell Universal to use the integrated mode" after upgrading to 2026.3.0

Description of Issue
After upgrading our PSU Dev instance from 2026.2.0 to 2026.3.0, dashboard apps that call Get-PSUCache -Integrated intermittently fail with:

You must be running this command in PowerShell Universal to use the integrated mode.

This confirms -Integrated is required for these calls to function (they were designed to bypass the Management API's role/token auth entirely), and that the integrated back-channel itself is broken/flaky, not the calling code.
Steps to Reproduce

1. On a 2026.3.0 instance, create/use an app (New-PSUApp) without -GrantAppToken.
2. In the app content, call Get-PSUCache -Key '<AnyCacheKey>' -Integrated for several distinct keys on page load.
3. Reload the app/page repeatedly.
4. Observe intermittent failures on arbitrary -Integrated calls with the error above — not on every load, and not consistently on the same call.

Expected Behavior
-Integrated calls made from inside a running PSU app should reliably execute against the same server process without needing Management API auth, regardless of load timing.
Actual Behavior
The integrated back-channel intermittently fails to establish/verify, causing the cmdlet to conclude (incorrectly) that it isn't running inside PSU.

Let me know if you need anything else from me.

Cheers