As we just roll back the change recorded in the vid above, here is the code change that breaks the editor:
Before = works fine:
<!-- wp:uagb/post-grid {"block_id":"ee2151b4","categories":"99","postsToShow":20,"displayPostDate":false,"excerptLength":27,"displayPostAuthor":false,"displayPostComment":false,"imgSize":"full","ctaText":"Read More","btnHPadding":0,"btnVPadding":0,"borderColor":"#ffffff","columns":2,"bgColor":"#ffffff","titleColor":"#ef5523","titleTag":"h1","titleFontSize":20,"titleLineHeight":1.1,"excerptColor":"#313131","excerptFontSize":14,"excerptFontWeight":"400","excerptLineHeight":1.2,"ctaColor":"#ef5523","ctaBgColor":"#ffffff","ctaHColor":"#313131","ctaFontSize":16,"ctaFontWeight":"100","contentPadding":10,"titleBottomSpace":20,"metaBottomSpace":2,"excerptBottomSpace":0,"paginationMarkup":"empty"} /-->
After = breaks editor
<!-- wp:uagb/post-grid {"block_id":"77bce79a","categories":"99","postsToShow":20,"displayPostDate":false,"excerptLength":27,"displayPostAuthor":false,"displayPostComment":false,"imgSize":"full","ctaText":"Read More","btnHPadding":0,"btnVPadding":0,"borderColor":"#ffffff","columns":2,"bgColor":"#ffffff","titleColor":"#ef5523","titleTag":"h1","titleFontSize":20,"titleLineHeight":1.1,"excerptColor":"#313131","excerptFontSize":14,"excerptFontWeight":"400","excerptLineHeight":1.2,"ctaColor":"#ef5523","ctaBgColor":"#ffffff","ctaHColor":"#313131","ctaFontSize":16,"ctaFontWeight":"100","contentPadding":10,"titleBottomSpace":20,"metaBottomSpace":2,"excerptBottomSpace":0,"postPagination":true,"paginationMarkup":"empty"} /-->
Hope this helps to replicate the issue…