WordPress 5.3 causes MB blocks not to load – JS error

After upgrading to WordPress 5.3 (no changes to my metabox blocks), none of my metabox blocks show up in Gutenberg. When opening a page that already has metabox blocks on it, it shows instead of the block: Your site doesn’t include support for the “meta-box/twt-featured-text-block” block. You can leave this block intact or remove it entirely. On the frontend, the blocks are still rendered correctly though.

When looking into the console, it shows the following error:

Uncaught TypeError: Cannot read property 'extend' of undefined
    at Module.<anonymous> (blocks.min.js:1)
    at n (blocks.min.js:1)
    at blocks.min.js:1
    at blocks.min.js:1

Here is the code in blocks.min.js that throws the error:

    $.extend(FormSerializer.patterns, {
        validate: /^[a-z][a-z0-9_-]*(?:\[(?:\d*|[a-z0-9_-]+)\])*$/i,
        key: /[a-z0-9_-]+|(?=\[\])/gi,
        named: /^[a-z0-9_-]+$/i
    }),

Thank you for checking into this!