Gameplay bug. Shaco boxes stop malph's ult

I am a malph player and I love this champ because his ult is extremely good in teamfights and it cannot be stopped by controls. However, one day when I ulted a shaco, i was stopped in the middle of the way. My friend told me that if u try to pass two shaco's boxes, u will be stopped whoever u are. And i tested it and it do stop things like malph's ult; J4's eq; etc. If it is designed like that, it makes sense on other champions but those like malph and sion who are written unstoppable can be actually stopped. I think this bug should be fixed as soon as possible.