Custom Anim Node: float property not updating

Hello,

I having problems coding a custom AnimNode.
In particular the following property is not getting updated.

UPROPERTY(EditAnywhere, Category = SkeletalControl, meta = (PinShownByDefault)) mutable float BlendWeight;

I have a simple Animation Blueprint, with uses my Custom Animation Node:

And a (local) variable ‘Blend Weight’ which is changing continuously between 0 and 1,
and which is assign/connected to the ‘Blend Weight’ Pin of my Custom Animation Node.

But for some reason the changes are not propagated/updated inside the Animation Node:

Can someone please point me in the right direction or tell me what I am doing wrong?!