I experienced the same error on multiple sites (ACF pro v5.9.4 in combination with WP core v5.5.3 – (update to WordPress v5.6 fixes it)).
I’ve just tested your fix (on local hosted sites) by downloading the acf-pro-blocks.min.js file and copy/pasting this in my pro/assets/js/ folder. However this doesn’t seem to have fixed the issue (tried this in 2 different websites so far).
Hopefully Ross and others can test the fix as well.
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