Supporting Fire unusable after 2 and a 1/2 uses

Not sure when this bug started, I've used supporting fire before without any issues.

Currently using supporting fire, the skill works fine the first 2 times and then the 3rd time I try and use it the skill fires a single volley and the skill becomes greyed out. The skill description with damage details disappear.

Switching weapon sets seems to fix the bug, but forces it to recharge its base cooldown(isn't taking into account my minion command CDR).