my divine ire keeps uncasting and recasting instead of channeling

Sometimes when i cast divine ire it just auto interrupts instead of charging up stacks. i hold the mouse or Q or whatever i assign it to, and it simply doesn't work. i have enough mana and health to cast it as it cost only 4 health and 4 mana.

At first i thought it was because i block but it happens even with no enemies or hazards around

here is a recording of the problem
https://youtu.be/W7Xar9RD4fw