bug: page flashes, never fully loads

[arena]

I was exploring the OpenStax Assignable platform and ran into a bug on the website.

To reproduce:

1. Using Firefox on a mac (and maybe any other browser) go to https://openstax.org/assignable
2. Click the button labeled "Start the process"

Expected: some sort of not flashing page explaining how to install/connect the tool

Actual: a flashing LMS selector widget that never loads and continually flashes