4.9.7 Dashboard not loading properly after migrating from subfolder to root

I just read about the SCRIPT_DEBUG define on this page:
https://codex.www.ads-software.com/Debugging_in_WordPress
It seems that loading

the “dev” versions of some core CSS and JavaScript files rather than the minified versions that are normally loaded

fixes the dashboard. Now I need to understand how to disable SCRIPT_DEBUG and enable CONCATENATE_SCRIPTS without breaking the dashboard.

Not as good as I thought. The dashboard page & post editor is still broken. See this picture.
The article content appears “blank”. I see it when I select it (but it was left out from my Ubuntu default screenshot tool).

Any pointers appreciated! ??

Following up… ??

I enabled logging debug information in wp-config.php

// Enable WP_DEBUG mode
define( 'WP_DEBUG', true );

// Enable Debug logging to the /wp-content/debug.log file
define( 'WP_DEBUG_LOG', true );

// Disable display of errors and warnings 
define( 'WP_DEBUG_DISPLAY', false );
@ini_set( 'display_errors', 0 );

// Use dev versions of core JS and CSS files (only needed if you are modifying these core files)
define( 'SCRIPT_DEBUG', true );

I got no output while browsing the dashboard’s editor. I checked that logging worked by adding these lines to my child theme’s functions.php (from this thread)

if (!function_exists('write_log')) {

    function write_log($log) {
        if (true === WP_DEBUG) {
            if (is_array($log) || is_object($log)) {
                error_log(print_r($log, true));
            } else {
                error_log($log);
            }
        }
    }

}

write_log('THIS IS THE START OF MY CUSTOM DEBUG');

Output was indeed written to debug.log. But now I don’t know where to look next…

I diffed a local backup from before migrating with the live version and noticed some differences in minified css and js files in wp-admin/ and wp-includes/.
Replacing these entire folders with fresh 4.9.7 versions fixed everything.
End of story. ??