Mostly doesn’t work

I found this plugin yesterday when I realized the one I’d been using was no longer supported. This was easy to set up and worked right out of the box.

Today I took a look at a couple of pages and they mostly don’t work. The first time I loaded this page it did, but then when I refreshed it didn’t any more: as the site loads the spoilers are visible, then they close and are impossible to reopen.

Is there some additional setting or site requirement to get this to work consistently?

The page I need help with: [log in to see the link]