Missing test parameter error on block creation

When adding an A/B test block, I can't seem to add of change anything on initial load and the default content isn't present:

I'm getting a `Missing test parameter` in the console.

When I do a full page refresh everything works.

Here is a video breakdown:

https://www.loom.com/share/64ac1e0516f544e6a82603d27b1df63b