I have a weird issue. First, some environment information:

Windows 10 Enterprise, 64-bit; fully patched and updated (current branch)
Kixtart (wkix32) 4.66
Domain joined
Logged on as a Domain User; User is a Local Admin
User Account Control (UAC) is turned off (never notify)

I have a custom registry setting I need to update: HKLM\software\firm\variables | test="1" (reg_sz) during the running of the Logon Script.

My logon script code looks like this: $_ = writevalue("HKLM\software\firm\variables","test","1","reg_sz")
The result (@error) is 5 (access denied) and the entry is not written (obviously).

BUT if I run a REG ADD "HKLM\software\firm\variables" /v "test" /d "1" /t "reg_sz" /f

in a cmd window, the result is 0 (success) and the entry is written.

The command is successful on both an "elevated" and a "non-elevated" cmd.exe.

I also have a Group Policy in place to modify the ACL of HKLM\software\firm to "Administrators: Full Control". These permission are propagated down to all sub keys and values. Registry hive permissions have been verified in the GUI.

Is there a bug in the WRITEVALUE function in 4.66 or am I missing something?