Early on in our WordPress development we were still figuring out the best way to make updates to blocks without causing issues for existing instances of the block. That means you might occasionally encounter a block that looks fine when you view the page, but appears broken in the editor with the warning, “This block contains unexpected or invalid content.”
Not to worry! There is an easy fix for this issue: There are three dots to the right of the broken block and if you click on those, you can click on Attempt Block Recovery, which usually does the trick!
Luckily, we’ve learned a lot about WordPress over the past two years and this no longer happens when we make updates to blocks. If you encounter any issues with block errors and are unable to resolve it yourself, feel free to firstname.lastname@example.org and we’re happy to help out!