I have critical error too. All updated on new version.
I was installed just Meta Box main plugin and when I activated the AIO, it get's criticall error and web will go down.
An error of type E_ERROR was caused in line 38 of the file /home/dev_collagen/public_html/wp-content/plugins/meta-box-aio/vendor/meta-box/meta-box-builder/meta-box-builder.php. Error message: Uncaught Error: Class 'RWMB_Loader' not found in /home/dev_collagen/public_html/wp-content/plugins/meta-box-aio/vendor/meta-box/meta-box-builder/meta-box-builder.php:38 Stack trace: #0 /home/dev_collagen/public_html/wp-includes/class-wp-hook.php(287): mb_builder_load() #1 /home/dev_collagen/public_html/wp-includes/class-wp-hook.php(311): WP_Hook->apply_filters() #2 /home/dev_collagen/public_html/wp-includes/plugin.php(484): WP_Hook->do_action() #3 /home/dev_collagen/public_html/wp-settings.php(557): do_action() #4 /home/dev_collagen/public_html/wp-config.php(90): require_once('/home/dev_colla...') #5 /home/dev_collagen/public_html/wp-load.php(37): require_once('/home/dev_colla...') #6 /home/dev_collagen/public_html/wp-login.php(12): require('/home/dev_colla...') #7 {main} thrown
