This might be related to Tip The Scales. Or to the JEI update that allows multiple pages to be shown at once.

Everything works fine at the Auto scale: https://i.imgur.com/klGT58A.png

But medium scale renders nothing: https://i.imgur.com/7TNXvA3.png
I guess it could be rendering, but only in the middle between the two previews?

It kinda works on a small scale, though: https://i.imgur.com/zg6yhrK.png
Though, I can't manipulate the preview at all on the small scale.

Similar here

Fix was already merged, as listed above. Wait for next release.

Cool!

Most likely related to said mod then. Try again without it and see if the behavior changed.

The bug still happens without Tip The Scales, I tried it