To make sure always the newest version of a preview container in tag manager is served, we should prevent the caching in the browser. For the apache version see matomo-org/matomo#13977
Header set Cache-Control "Cache-Control: private, no-cache, no-store" for ^js/container_.*_preview\.js$

Otherwise the user will need to use ctrl+r or something to reload a page that includes a preview file to make sure the cache is ignored and many users would not know that.