[GAMEPLAY] Soraka's Q not Functioning Properly in URF

Every once and a while Soraka's Q does not do damage or refresh the slow. I have only come across this in Urf, and it only seems to happen when I try to cast it immediately off cool down after an initial, working, Q. The casting animation occurs, and the spell goes back on cool down.

Step 1: Play URF mode Step 2: Pick Soraka Step 3: Cast Q on enemy champion, creep, or neutral monster. Step 4: Cast Q again immediately off cool down

It has worked many times, but occasionally it doesn't - if I had to guess; it occurs 1 in every 15 or so Q's. I mostly only notice it when I am farming creeps, and is probably the easiest way to see it. If it has occurred in a fight with a champion I am too caught up to notice.