(It’s been so long since I last looked into the bug...)

> It doesn't happen in emacs-26, which has the same
> electric-pair--with-uncached-syntax call, so it's not just that alone.
> I suspect this could be related to the recent changes to mark ">"
> outside of tags with punctuation syntax (technically, <foo>a > b</foo>
> is valid, only "<" needs to be escaped as &lt;).

You’re right.  The problem is that electric-pair--with-uncached-syntax
let-binds syntax-propertize-function to ignore, causing the syntax of
">" to not be updated.

Applying the attached patch fixes the issue.  However, in what cases
would we want syntax-propertize-function to be let-bound to ignore?

Best regards,
Dario