Since the 1.11 update, when I bring up the challenge menu, two of the apprentice rank challenges are missing an icon and cannot be completed: the Cactus and Melon challenges. The box where the icon should be is blank; nothing appears when I hover over the box; clicking on the box does nothing. I have rebooted, I have removed resource packs... no change. Curious.
Yep, and a number with silly abilities like remembering we saw something, somewhere, about some aspect of game play! That's why it's fun to ask a question like this.
Just to add to GrimpyHalfhand's point - the counters on the challenges seem to have stopped at 64 as well. I can continue completing challenges above 64 but the counter doesn't change (lower level counters continue to add numbers as I complete them).