/cqs is functionally broken. It does not cancel any queued spells and is causing a major headache for mouseover spells. A spell being queued (your cursor is outlined in blue) is preventing me from casting additional spells OR tab targeting until I clear the queued spell.
I don’t know if this is intended mechanics, but tab targeting while a spell is queued will begin casting on the new target, but also prevent any further tab targeting.
I suspect this may somehow be related to the new targeting mode, which, no, I do not have turned on.
I also have 0 addons enabled and my warrior friend (I’m an evoker) has the same issue.