I'd just like to warn people that switching to another theme could potentially be detrimental to your site. Be sure to make a backup first!

Particularly if you have widgets in non-standard positions it could erase all your widgets.

Also, if you have renamed your page template it is saved in your database. You can use wp-cli to do a search and replace:

wp search-replace 'old-page-template' 'new-page-template' --skip-columns=guid