Malzahar Ulti direct to cooldown bug

into Playing Malzahar against a Katarina. Malzahar Ulti went straight to cooldown without casting when (it seems) it was cast at the exact moment that Kat jumped. Happened twice in the same game, when I was not the focus of the fight, without being affected by any CC myself - no stun, no silence, no fear, could still move, just ult was instantly on cooldown. I did not click to move during the ult, I did not double click the ult, I did nothing to break the suppression early.

Is there possibly a bug whereby Katarina momentarily ceases to exist on the battlefield, breaking suppression (which, if cast successfully, should prevent her from moving, and if she managed the move, then the spell should not have gone to cooldown as it had no target to resolve on)?

I am sure about 2 of the fights, as I was not the focus of the fight I had time to look and ask myself why my ultimate was not suppressing the Kat as I had cast it at that same moment. It may have also happened under my tower while I was being ganked, but I cannot be sure that I didn't break the tether myself while under pressure.

Also, this caused a loss in a critical game (following 2 games with 4v5s in a row due to bad servers causing DCs) and thus demotion.