A single Rise block that I've used in several Rise projects is now suddenly not loading

Hi, I've been creating several different variations of a Rise project, making separate copies over the last few days. A single Rise block that I've used in several Rise projects is now suddenly not loading. Aside from text, the block contains an interactive tab table and a quote section from the included Wellness sample course. When previewing or trying to edit that block, I get a blank page. Refreshing the page shows me a screen that says I edited it XX hours ago and asks me to Take control. Taking control does nothing - brings me back to a blank page. All the copied and edited projects (three of them) have this issue in the same block. The rest of the blocks/lessons work fine.

The corresponding block in the sample course is "Managing Stress" and it is showing the same behaviour when I try to edit or preview it.

I've logged out and back into Articulate360 and rebooted my computer. I'm using Chrome.