OnePress Theme too demanding on admin-ajax.php

Hello,

I’ve been using the OnePress theme for the past 4 years now with mostly no issues until recently. For whatever reason the OnePress theme is crashing the website and database. When I deactivate it the website works as normal. It seems to be lagging the admin-ajax.php leading to an error 503. When it does temporarily work it slows down the website and eventually just crashes again. Is there anything I can do to fix this?

Thanks

The page I need help with: [log in to see the link]