I resolved the issue by deleting the cache at /min/cache/*
.
It would have contained information created from the original website prior to the updating to the latest version of the Enfold Theme.
Unsure why Enfold wouldn’t clear this after related options are updated – maybe it does and there is a lingering issue?
You may need to toggle or temporarily disable the Enfold > Performance > File Compression settings to reload the scripts and stylesheets, and make sure to update any modified template files in the child theme. Please do not forget to purge the cache afterwards.
The Enfold > Performance > File Compression options for CSS and JS were disabled. I enabled them, cleared the cache and force refreshed the staging site – the navigation still displays incorrectly so I set the Compression options back to disabled and cleared the cache again.
There was no Child Theme with the original site and \wp-content\themes\enfold\css\custom.css has no custom css. Appearance > Customise: Additional CSS has one entry relating to table styles but no navigation elements.
Any suggestions for what I should investigate next other than trying to find the original theme files and performing a filediff on the production files to see if the original developer hard coded an update? (I doubt this as I’m sure a visual editor is the limit of his capability).