Pricing block text size changes lead to invalid content

When adding a Genesis Blocks pricing block and attempting to change the font size of one of the products in the pricing table, the result is an “invalid content” message that cannot be recovered from the next time you try to edit the page.

I created an animated GIF showing this on a test page:

https://www.dropbox.com/s/8xk79br3zuyugly/genesis-price-block.gif?dl=0

Steps to reproduce:

* Create a new page
* Add the pricing block
* Select the product title
* In the “Text Settings” dialog, change the “Font size” to something like Large
* Save/Publish the page
* Exit and then reopen the page editor
* Notice the message, “This block contains unexpected or invalid content”
* Notice that after “Attempt Recovery” and a save, the problem repeats

Let me know if you need anything else to take a look. Thank you.