When clicking the search bar in JEI, the focus is lost immediately, not allowing anything to be typed.

Everything else in JEI works fine, recipes, uses, paging through items. Search is just nonfunctional.

Are you sure this issue is related to Rubidium? Maybe you have any addon for Rubidium?

I do have Rubidium Extras, but I removed it prior to writing this issue to see if that was the cause. After removing it, the problem still persisted.