5v5, mordekaiser BUG "W--circle disappears mid-game"

I thought it was my computer but even my friend have the same problem. After about 15 minutes of the game ill activate my w and notice that the circle on the ability is totally missing even when i put it on a ally or minion. The only way to fix this issue is to relog and even then it does it after 5mins. The build i go is dark seal into a hex then a deadman , maybe those items makes it lag combine but please fix. In team fights i never know if my ability is over or not.