I’m sure you’ve gotten this fixed by now, but just wanted to chime in that this was not an issue with Advanced Custom Fields. It was an issue with Events Calendar and their update. It not only broke ACF, but dozens if not hundreds of other plugins that use the Select2 js library.
They were made aware of it pretty quickly with tons of support requests and released a patch that fixed the issue. If you still don’t have it working I’d suggest contacting Tribe Events Calendar, as their plugin is the one that broke things.
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