UPDATE (june 26 2019):

We do not have Gutenberg plugin installed.

I can provide the wp-admin and FTP access. Tell us where to send you the credentials.

Upon accessing some of the menus from the WP dashboard pages, it will load a white screen of death "The site is experiencing technical difficulties. Please check your site admin email inbox for instructions."

This is only affecting our 'BETA' staging website, but not on our LIVE website.

Upon checking the email it displays the following error details:

An error of type E_ERROR was caused in line 2884 of the file /home/yesalingles/public_html/beta/wp-content/themes/thegem/functions.php. Error message: Uncaught Error: Call to undefined function gutenberg_can_edit_post_type() in /home/yesalingles/public_html/beta/wp-content/themes/thegem/functions.php:2884
Stack trace:
#0 /home/yesalingles/public_html/beta/wp-includes/class-wp-hook.php(286): thegem_gutenberg_replace_default_add_new_button('')
#1 /home/yesalingles/public_html/beta/wp-includes/class-wp-hook.php(310): WP_Hook->apply_filters('', Array)
#2 /home/yesalingles/public_html/beta/wp-includes/plugin.php(465): WP_Hook->do_action(Array)
#3 /home/yesalingles/public_html/beta/wp-admin/admin-header.php(125): do_action('admin_print_scr...')
#4 /home/yesalingles/public_html/beta/wp-admin/edit.php(353): require_once('/home/yesalingl...')
#5 {main}
  thrown

We have two websites working independently and are identical except for the WP and plugin versions. One website is live (in production) and the other is beta where we test changes. We currently have a live website that has an older version of WP (v. 5.0.3) and the plugins were not updated recently. And the beta version has the WP (v5.2) with all of the plugins updated. 

We narrowed it down to the specific error regarding the 'Gutenberg'  functions.

Is there a way to temporarily disable the Gutenberg function. We might think that it may have something to do with the different versions of WP between the two websites, but can't find a solution after going through several forums and fixes on GitHub.

Thanks.