Hello @Matthias Veelaert
Usually the main issue when running PSEXEC when elevated permissions are required is that either UAC is enabled or the syntax is not adequate.
Please try disabling UAC: https://learn.microsoft.com/en-us/troubleshoot/windows-server/windows-security/disable-user-account-control
Use the –h switch to indicate that PSEXEC will use elevation for execution. Reference: https://learn.microsoft.com/en-us/sysinternals/downloads/psexec
Hope this helps with your query,
---------------
--If the reply is helpful, please Upvote and Accept as answer--