After Build 42 in 2.55, Whistle Whirlwinds have some buggy interactions. And it looks like it is a side effect of changes to ->Level
With a Level 1 Whistle, the Whirlwind will disappear when it moves over a Warp Return, even without touching Link first.
At higher levels, it works normally on the screen you summon it on. However, on the destination screen if will miss the drop off on the warp return square. If it is moving right, it will drop the player off on the rightmost combo. Otherwise, it will scroll to ANOTHER screen (I think next or previous in the warping sequence) and then drop the player off correctly. I also notice the Whirlwind sprite changed to the Whistle 1 sprite after this extra transition.
Happens in Builds 45, 47, 48, and 50.