Word not ignoring unavailable .dot template in .doc

[Peterson]

Four users are collaborating on an old .doc file, created with a long-lost template, with Automatically update document styles ticked. (Yes, I know this isn't ideal; I can't control their use of the file.) All users are on enterprise Office, current build; all Win10.

Three users can open/work in the file without issue: Word ignores the link to the non-existent template and doesn't try to update the styles; the formatting is preserved.

But Word throws an error for the fourth user: "Sorry, we couldn't find <the long-lost template>. Is it possible it was removed, renamed or deleted?" After OK is clicked, Word attaches the Normal template, updates the styles, wrecks the formatting.

When I and a colleague open the file, we also have no issues with it -- Word is ignoring the non-existent template/auto-update.

I've looked through all of the settings in Options and can't see anything that might affect whether or not Word "phones home" for the template, and I'm coming up short on web searching.

Any idea what's going on?