Having an action/attack cancel midway through cast

I was in A1S and have had this happen several times when I go to cast an attack on the oppressor at the split and I was standing still when shooting and the cast cancelled half way through and I was not moving at all. I understand that if you move the cast cancels because I have played blm and smn to understand that concept but I was standing still. Oh I forgot to say this is happening on bards. Please fix this or even better get rid of the cast bar on bard/mch.