Modal dialog frozen

Problem/Motivation

We are using D10 with this theme and CiviCRM. Modal dialogs are frozen, i.e. none of the fields or the scrollbars work.

Steps to reproduce

Install D10.
Install CiviCRM.
Install Flexistyle.
Go to an object to show a modal dialog, e.g. adding a membership.

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes