Steps to reproduce the issue

As soon as I run the update for Joomla 3.6.3 from Joomla 3.6.2 I get this error on the front end of said website. I have had to restore the site to an earlier version of Joomla

Expected result

The core gets updated

Actual result

Core is updated and Admin (back) end works, but frontend of site is broken (see screenshot attached)

System information (as much as possible)

See screenshot below

Additional comments