Ignite constantly fails

At least once a game I ignite someone and it just does not work. I cannot count the times that I have attempted to use ignite on someone and it just fails to go. Sometimes I have to press it two or three times in battle to get it to go off. Either the hit box of the champion is so hard to track that the mouse is slightly not touching them when I release the ignore spell, or there is something wrong with it entirely. Again, countless times I have attempted to ignite someone and it just fails to work properly. I can't be the only one with this problem. I suggest increasing the radius around champs that ignite can target. Thank you.