When I get to add new custom fields The "fields" and "settings" tabs only show "loading fields/settings, please wait"
But they never load. In the error console the only thing showing are three json errors: Uncaught (in promise) SyntaxError: JSON.parse: unexpected non-whitespace character after JSON data at line 1 column 218 of the JSON data
repeated for column 470514 and column 1953
thank you I had done that already however it turns out that it was a php warning which I had erroneously dismissed as not relevant. One of the other plugins which I had already deactivated, required allow url include and metabox won't work properly if this is enabled. Disabling it resolved the issue.
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