Shopify theme requiring updates for full compatibility

Hello,
We have been experiencing several critical issues with our Shopify site that uses the x.shop theme.
We called Shopify to read them the riot act last week, and they let us know that the issues being experienced actually tie back to the need for key parts of the theme to be updated, so as to be able to best work in Shopify's updated environment.
Please advise how we can get this fixed. Thanks!