hotspot anchoring on image bottom

hi, i 've got a simple hotspot like

<hotspot name="hs_01" url="fern.png" ath="-35" atv="20" edge="bottom"/>

an downward pointing arrow, which should alway point to my poi, defined by ath and atv. the tip of the arrow in the png-image is located on the bottom edge. when i'm zooming in the player with this hotspot definition, the arrow is always wandering and not anchored to the ath/atv.

what's wrong with my hotspot?

example in the attached images

thanks,

Ja ich kenne die Doku. Nur funktioniert mein Beispiel eben trotz edge auf bottom nicht. Habe es ja oben schon gesetzt und trotzdem ankert der Hotspot im Zentrum.

Habe nur ich das Problem?