Theme is broken in places, help!

I’m trying to use Hestia to update a current website. It’s all worked fine in a test environment, but my client installed a really old version of Hestia on the production site previously, and adding the latest version is causing loads of issues with sections (via the customiser) not being editable, when clicking into the Pro section (I am just running the free one) I just get presented with PHP code.

It is clear I need a clean start, but deleting an reinstalling the theme does nothing.

Anything else I can do? This was meant to go live today, I’ve lost hours of time!