In the html source itself the … is getting converted to “…” so it’s getting yet another html sequence escape when it doesn’t need it.
Always backup themes before making any customizations.
Search the collection template for the pagination, or pagination snippet.
Your looking for “…” or it’s translation key equivalent, e.g; {{ ‘general.pagination.ellipse’ | t | escape }}.
It’s likely either a custom string was added to the translation key itself so the ampersand gets escaped, or is an additional escape filter and it may either need to be removed or replaced with escape_once
You could also try getting a new install of the same theme version and checking if the behavior is a bug in the theme itself , if so contact the theme devs.
But if you cannot find any of the above you probably need to hire someone to dig for the problem and fix it.