Unerring Power support gem not working with huntress combo.

The combo: Whirling Slash x3 > Barrage > Twister

When using the combo with the Unerring Power gem (socketed into Twister), the Twisters consume the Whirling Slash but don't get buffed.

This happens the majority of the time, but it does randomly work. I am able consistently to recreate the bug, when standing still and performing the combo.

Has anyone else run into this bug, or is able to recreate it?