[Gameplay] Channeled or likewise ults being canceled as if a basic attack/move command was input

In the last game I played with one of my teammates I usually played with she encountered a bug she'd been frequently experiencing, particularly on Miss Fortune. She begins her ult animation, only to have it canceled immediately, not on purpose. No damage done, put on full cooldown.

Working on how to reproduce it, as it hasn't happened for every single MF ult (or similar champion).

Working on video/screenshots, and it happens roughly 25% of the time. Noticed it starting to happen roughly patch 6.2

I apologize for the lack of evidence, but will include further information.

Currently my teammate is using a laptop (Gateway NE56R31u) and a wacom tablet instead of a mouse, they are going to be switching to a more reliable desktop that could potentially record gameplay roughly tomorrow and I'll try to update the post.