(This affected every Game mode and every Version)
I was playing MC (with mods, but that's irrelevant in this bug.)
I walked into a new biome, and tried to select my shovel from my inventory, to drag it into the Hot Bar.
To my surprise, it wouldn't move without me holding down the left mouse button.

This is much less 'game breaking', but it's something that annoys me, as it means I must have an empty inventory at all times, as It wouldn't swap items at all.
What's even more worrying is that it done the same thing on a game without mod
I would very much appreciate your advice on the matter, and that you might try to fix the problem.

From Sparks