Your experience seems to align with my theory (June 14):
My working theory is that removing S Mode may require the same sort of security as other, usually-paid, license upgrades.
This likely requires certain security files, or certificates, to be valid.
It may be that, for machines that were imaged months or years earlier, carry with them an old, likely expired certificate. That is what blocks the "license change" from initially being executed. However, there may be a process that periodically checks the validity of the security certificates, and if out of date, refreshes them with currently valid replacements. It also seems possible that reinstalling Windows from a recently downloaded ISO file/disk installs currently valid certificates.
So, perhaps there are two ways for this problem to resolve. Out of date certificates that prevent the "OS Change", i.e. Exit S Mode, get replaced with fresher, currently valid certificates using one of two methods:
- Install from an image downloaded close to the time you wish to exit S mode.
- Wait one (or more) days, and the outdated certificates are automatically replaced.