Upon reviewing the error message, it appears to be linked to your child theme of bb-theme. While it's uncertain whether your theme is the root cause, conducting a conflict test with your theme could help us pinpoint the issue.
To proceed, could you please enable maintenance mode on your website and switch to default themes such as twenty twenty four or twenty twenty three? Then, assess whether the issue persists. If it disappears with the default theme, it suggests a conflict with your child theme of bb-theme. However, if the problem persists even after switching themes, it's likely related to our WPML plugin or a third-party plugin. Please inform me of the results of your test.
After clearing wp cache, object cache, and W3 Total Cache cache, and a couple of browse refreshes I can get the Appearance -> Menus to work properly.
This tells me 2 things:
1) There is no plugin conflict unless the conflict is with W3 Total Cache
2) This is a cache issue between WPML and WP and W3 Cache
I have disabled WPML's "Cache for Language Switcher Templates" in WPML Support "Advanced Settings" to see if it does something.
