Hello @DAN NABET
It is indeed strange, and the fact is that you should be able to edit those policies as administrator. I wouldn't discard that there are other management and administration issue on this computer, so in case of a enterprise environment you may want to look into saving user data and reimaging.
In your case, the only workaround I can think of is to reset all Local Policies using an elevated command prompt and run:
RD /S /Q "%WinDir%\System32\GroupPolicyUsers" && RD /S /Q "%WinDir%\System32\GroupPolicy"
then run a gpupdate /force to load the domain GPOs
If you get any access denied error or 0x5 that would mean that your user has not enough privileges to manage local policies.
Hope this helps with your query,
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