Hey There,
I have logged in and edited a few pages in your site. I do not have issues loading the pages in the Editor. When I check the console, I could replicate the error. Though I still see the warnings and another JS error too. Did you already edited your wp-config.php file and added the PHP memory limit and PHP max limit? If not, please do. please edit your wp-config.php file and insert these lines:
define( 'WP_MEMORY_LIMIT', '256M' );
define( 'WP_MAX_MEMORY_LIMIT', '512M' );
And you could also try testing for a plugin conflict. You can do this by deactivating all third party plugins, and seeing if the problem remains. If it’s fixed, you’ll know a plugin caused the problem, and you can narrow down which one by reactivating them one at a time.
Please let us know how it goes.