Given this code block:

<!-- wp:code {"highlightedLines":"2","showLineNumbers":true} -->
<pre class="wp-block-code"><code>if ( true &amp;&amp; false &amp;&amp; 1 &lt; 0 &amp;&amp; 0 > 1 ) {
   // Unreachable &lt;code>!
}</code></pre>
<!-- /wp:code -->

In WordPress 5.5 when Gutenberg is not active, this renders in the editor successfully:

However, when Gutenberg v9.1.1 is active, block validation errors occur:

Block validation: Expected text `if ( true && false && 1 < 0 && 0 > 1 ) {
   // Unreachable <code>!
}`, saw `if ( true && false && 1 < 0 && 0 > 1 ) {
   // Unreachable <code>!
}`

This did not happen in Gutenberg v9.0.0. It starts to break as of v9.1.0.