For running J!5.1 you must https://fabrikar.com/forums/index.php?wiki/update-from-github/ or include the new file manually https://fabrikar.com/forums/index.php?threads/joomla-5-1-and-fabrik-cannot-find-files-error.54473/post-285151 See also Announcements
Please see our announcement here.
Watched values are correct.main.js?65eb9b69:1 [Deprecation] Listener added for a synchronous 'DOMSubtreeModified' DOM Mutation Event...\
Yes, there are still issues with the usekey feature in general (not only CDD related)user_id by setting the row_id to -1.