404 error on frontend editing

HI

The site is built using the Kidzy template version 3.0.0
PHP 8
Joomla 4.2.6
It was upgraded from a J3 site

1. Above article titles we get a funny ?> symbol (see https://ettingtonpreschool.co.uk/information/curriculum)

2. When we login to the front end and try to edit anything we get the 404 error page with

behavior::modal not found.

Please can you login to the front end to test this (try editing an article i.e. https://ettingtonpreschool.co.uk/information/hours-and-fees ) to recreate the error.

And help us to resolve this please as we want to be able to edit via the front end.

Thanks