Kayle Ult

This has been ongoing and getting data for this is difficult on my end. I normally have approximately 60ms latency. I don't know if this is latency related or not but, the R (ult) on Kayle sometimes fail to work. It usually occurs during team fights. Sometimes it appears that if there is enough champs damaging Kayle at the same time it will fail. Not always but it does happen. This could be particular so a situation that i am unaware of. It will go on cd and not appear to work at all. I've always thought this to be latency related but want to make sure. I have been reluctant to play Kayle because of this.