Sentinel's Eternal Refuge - Secondary Effect bugged (for Druids)

[Gadoschi]

WoW Freakz link: https://www.wow-freakz.com/item_finder.php?item=146669&&name=the-sentinel-s-eternal-refuge
Bug description: The item's secondary effect (transforming into a wisp, granting increased movement speed and flying respectively) is broken for druids
How it should work: Once you've killed 5 enemies and when next out of combat, you turn into a wisp; if indoor, you can move at 100% ground speed; if outdoor, you can move at your flying mount speed and fly as if you were on a flying mount
Bug description:
1. once your movement speed reaches 5 stacks, whether you are indoors or outdoors, you will continuously and forcefully switch between spirit owl form and the form you were in when you got your 5th stack,
2. while the constant and rapid switching between your normal form and the spirit owl form is happening (this continues to happen whether I shift back to my normal form or remain shapeshifted), I am basically unable to do anything, as I cannot use my normal abilities nor fly using that weird spirit owl form, and am forced to cancel it by removing the 5 stack buff manually, which is incredibly annoying and negates the whole point of this item.

I could provide screenshots if truly necessary, but I believe this bug is very easily verifiable.

P.S. The item seems to be working fine on my Demon Hunter.