If you have the Scalia theme activated then if you temporarily Activate the Voxco Framework plugin to fix say an Owl_Slider element associated with that theme setup then you must remember to deactivate it afterwards else then the post/page/portfoilio item won’t show on the front end and give a Page not Found response.
To fix the Save Changes not working with WPBakery Page Builder when using WordPress 6.11 you need to install the Enable jQuery Migrate Helper plugin as well. The Save Changes should then work.
Must change all the portfolio items into posts with a plugin “Post Type Switcher” before switching the theme then switch them all back to being portfolio items. Scalia has a different enough portfolio system for them not to transfer across otherwise.
Where there are Owl_Slider widgets on a page can be better to delete everything and start again but:
The best way:
Activate the Voxco Framework Plugin so that the Owl Slider elements show in the backend editor.
Make notes in a word processor page of all the names of the .jpg images referred to in these elements where abouts they are on the page.
Delete the Owl Slider elements.
Deactivate the Voxco Framework plugin.
Refresh the back end.
View Portfolio Item to check that the bracketed shortcodes are gone.
Add Single Image elements as replacements with Full size and centre alignment.
Check front end.