Bug with Kalista's ult

I just finished a game where I could't use "Oathsworn" on my support properly. I would press 7 and attempt to bound my support but all you would happen is the sound of the ult and nothing else. I noticed that when I would attempt to ult my support, they would freeze on top of me and they couldn't be thrown. I have played her before and I know how to bound people, this has never happened to me before so it was very frustrating. The "Oathsworn" was kept in my build so I couldn't even get a 7th item even if I wanted to. Kalista is one of my favorite champs and it disappoints me that I couldn't play her to her full potential. -ThrenodialSoul