drupal_flush_all_caches is problematic.

Problem/Motivation

Many large sites build up a considerable amount of cache, they may use tools like Redis to manage many gigabytes of it, so clearing cache becomes a process that needs be handled carefully, so using drupal_flush_all_caches is just reckless and too large a hammer for this job.

Steps to reproduce

Have a big site, save a quicktabs instance, watch things crash.

Proposed resolution

Remove drupal_flush_all_caches and use tags or contexts based on the selected elements.
/quicktabs/src/Form/QuickTabsInstanceEditForm.php #303

User interface changes

Maybe just instruct the user to clear their cache if they aren't seeing their expected changes.