Ranking For Mobile But Not Desktop?

So I'm a bit stumped with this one. In the past this keyword jumped around between 1st and 3rd on desktop (same with mobile) and after the recent core update google started listing a different page as 97th (desktop), but is rank 1 on mobile (both show the same content and have "good" user experience).

I have now 301'd this page that was being shown on rank 97 (to the original) but there hasn't been any movement. The page seems to be indexed according to google search console but when I search site: <url> I can't see the page.

Has anyone had experience with something like this before?

Any help or insights would be greatly appreciated, thanks.