Thunderlord's double procing or procing again before full cd timer.

This is something I've seen before against other champions in recent patches but I kinda played it off as a visual bug but after my last game I am certain that it is not visual, but an actual gamebreaking bug allowing you to put out more damage than you should be. In my last game I was facing a top as . We had just finished trading blows and had all abilities and both of our thunderlords on cooldown. About 5 seconds after that trade he dashes onto me and procs thunderlords with another spell rotation while it was on cooldown which actually killed me (this is lvl 3 so tlords was around a 24 second cd.) Another fight a few minutes after that one he goes in with full spell rotation (e q r) and thunderlords actually plays the animation twice over about a half second span. I'm not sure what is causing this or how to recreate it but it seems like something that is exploitable because after I brought it up in all chat it stopped happening. I feel this needs to be looked into as it allowed him to get off extra damage that shouldn't have happened, in turn allowing him extra presence in lane.