Channelling skills keep casting after changing input

When going casting a channelling skill to another channelling skill without stopping either action in between, the second channelling skill is not cast, and instead, the first one keep casting.

Example:
Left Mouse Button - Fury of the Mountain (Bear form)
Right Mouse Button - Rampage (Bear form)

I click and hold the left mouse button to keep creating fissures. Then click the right mouse button and release the left mouse button (either 1. both these actions simultaneously, or 2. first clicking rmb then releasing lmb. either approach reproduces the bug, but 2. is more consistent), and I keep creating fissures. I don't start stomping.

If I'm already stomping (holding right mouse button), and change to holding the left button, I keep stomping.