When I try to cast sheep on a target infront of me then in mid cast i shimmer blink forward (making him behind me) cancels sheep cast or doesnt finish casting, but if i recast it it works ....not soo easy to explain

X --sheep---> Z -----still casting sheep then shimmer blink-------> Now Z is behind me and sheep cancels
^ __________ ^
me ________ target



just wondering why does it stop casting if the target is in range and sheep can be casted no matter where I am facing