Adding to this:

It may be related to dialog triggers. I had this occur during the last introductory campaign mission (the one with the wave defense). I had activated the ability just prior to a dialog cutscene starting. The ability was present in the cutscene and then continued with infinite duration after the scene. I was actually able to cast the ability again and had 2 active at the same time for a brief period (the 2nd one obeyed the expected cooldown).