Teemo shroom's not detonating when people pass over them [gameplay]

The bug I am talking about happened several times during the game but this was the first time it happened. People were walking, travelling across, or even standing on mushrooms without them detonating. There were no control wards or sweeping trinkets to disable them, they simply were not detonating as they should have. If a person is not untargetable when they cross the shroom, it should detonate, but didn't, unless someone can give me a little insight?