when Compose Requiem stop?

When the skill Requiem Compose stop?
i know when you :
- use potion
- use other skill
- music is finish

but sometimes i dont know why the skill stop
Yesterday I could reuse my skill after killing a rare monster (yellow) but today the skill often stops after killing the rare monster and sometimes it doesn't stop, I don't know what the condition is for the skill to stop...

It would be useful to include the conditions for interrupting the skill in the description.

do you know?

sometime it stops if i get hit, let's be honest tho, it's bugged and it shouldnt stop at all unless its duration expires.

need some fix or clarification.