Multi-App Kiosk Deployment Fails on Windows 11 Builds 26100.6584 & 26100.6899 with MDM response code 500 and event viewer Error 0x86000005

We are deploying multi-app kiosk mode on Windows 11 devices using the Assigned Access CSP (./Vendor/MSFT/AssignedAccess/Configuration). The same configuration (XML, AllowedApps list including both UWP and Win32 desktop apps) succeeds on build Version 23H2 (Build 22631.6060) and 24H2 (Build 26100.1742), but fails on 24H2 (Build 26100.6584) and 25H2 (Build 26100.6899), returning an MDM response code 500 and we also see errors logs under Event Viewer(Microsoft-Windows-AssignedAccess/Admin):

<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="Microsoft-Windows-AssignedAccess" Guid="{8530db6e-51c0-43d6-9d02-a8c2088526cd}" />
    <EventID>32000</EventID>
    <Level>2</Level>
    <Task>1001</Task>
    <TimeCreated SystemTime="2025-10-29T07:59:15.5522639Z" />
    <Channel>Microsoft-Windows-AssignedAccess/Admin</Channel>
  </System>
  <EventData>
    <Data Name="Custom">AssignedAccess Configuration failed</Data>
    <Data Name="ErrorCode">0x86000005</Data>
  </EventData>
</Event>

What we have tried so far:

• Verified XML syntax and included multiple schema namespaces (e.g. v3, v5, rs5, default 2017) Tried XML :

    <Sequence>
      <Replace>
        <CmdID>POL_KIOSK_MODE_REPLACE</CmdID>
        <Item>
          <Target>
            <LocURI>./Device/Vendor/MSFT/AssignedAccess/Configuration</LocURI>
          </Target>
          <Meta>
            <Format xmlns="syncml:metinf">chr</Format>
          </Meta>
          <Data>
    <AssignedAccessConfiguration xmlns:xs="http://www.w3.org/2001/XMLSchema"
                                 xmlns="http://schemas.microsoft.com/AssignedAccess/2017/config"
                                 xmlns:default="http://schemas.microsoft.com/AssignedAccess/2017/config"
                                 xmlns:rs5="http://schemas.microsoft.com/AssignedAccess/201810/config"
                                 xmlns:v3="http://schemas.microsoft.com/AssignedAccess/2020/config"
                                 xmlns:v5="http://schemas.microsoft.com/AssignedAccess/2022/config">
      <Profiles>
        <Profile Id="{9A2A490F-10F6-4764-974A-43B19E722C23}">
          <AllAppsList>
            <AllowedApps>
              <App AppUserModelId="Microsoft.WindowsCalculator_8wekyb3d8bbwe!App" />
              <App AppUserModelId="Microsoft.Windows.Photos_8wekyb3d8bbwe!App" />
              <App DesktopAppPath="%windir%\System32\WindowsPowerShell\v1.0\Powershell.exe" />
              <App DesktopAppPath="%ProgramFiles(x86)%\Microsoft\Edge\Application\msedge.exe" rs5:AutoLaunch="true" rs5:AutoLaunchArguments="--kiosk https://www.ibm.com/in-en/ --edge-kiosk-type=fullscreen --no-first-run"/>
            </AllowedApps>
          </AllAppsList>
          <v5:StartPins><![CDATA[{
            "pinnedList":[
              {"packagedAppId":"Microsoft.WindowsCalculator_8wekyb3d8bbwe!App"},
              {"packagedAppId":"Microsoft.Windows.Photos_8wekyb3d8bbwe!App"},
              {"desktopAppLink":"%APPDATA%\\Microsoft\\Windows\\Start Menu\\Programs\\Windows PowerShell\\Windows PowerShell.lnk"},
              {"desktopAppLink": "%ALLUSERSPROFILE%\\Microsoft\\Windows\\Start Menu\\Programs\\Microsoft Edge.lnk"}
            ]
          }]]></v5:StartPins>
          
    
          <Taskbar ShowTaskbar="true" />
        </Profile>
      </Profiles>
      <Configs>
        <Config>
          <Account>kioskuser</Account>
          <DefaultProfile Id="{9A2A490F-10F6-4764-974A-43B19E722C23}" />
        </Config>
      </Configs>
    </AssignedAccessConfiguration>
          </Data>
        </Item>
      </Replace>
      <Final />
    </Sequence>
    
  

  Deployed the same policy on devices with builds 22631.6060 and 26100.1742 (which succeeded) Confirmed the kiosk user account is in place and not blocked by MFA or conditional access policies Verified OS edition, license, and that multi-app kiosk is supported for those editions

Questions / Request for help:

1. Has anyone else encountered error code 0x86000005 or a similar multi-app kiosk deployment failure?

Is this a known regression in these builds for Assigned Access on Windows 11?

1. Are there any required hotfixes or workarounds (for example, adjustments to registry keys, changes in XML schema usage)?

Thank you in advance for any insights, experiences, or links to released fixes or recommended workarounds.

— Ujjawal (Software Developer)