Adding an effect to a PNG image with transparency

[smantik]

Hi.
I have a PNG image of a fly with transparency in a layer and below it I have another image of a paper texture that covers the entire screen. I can see the fly over the paper with no problem with an alpha 100% layer blend mode.
The problem starts when I use a Fragment Shake effect with the fly layer to animate it. If I change Fragments and Distace values the fly moves, but the transparent part of the layer becomes black and I can't see the paper that is below anymore.
If I move the Opacity slider of the effect, I can see the paper but not as white as it is without the effect over the fly layer.
I have changed the blend effect mode (50% modes, multiply, screen...) but I can't get a scene where the fly is shaking while the paper is white. It's like the transparency of my PNG image disappears with the action of the effect.

Is there any solution?
Thanks.

PD: using Resolume 5

[smantik]

Oh, my god!
If I use the same PNG image of the fly but with the background in black, I got the same result.
I think it is a bug in the effect Fragment Shake that uses the alpha space in the image as it was black. But it is strange, because if put another fly image with alpha under the first fly with no background, if I rise the opacity of the effect the second fly stays with the same luminance. But, if I put the background in the lower layer, then the second fly is getting darker when I rise the opacity of the effect!!!!
If I use another effect like Iterate Rotator, I have no problem with the alpha channel of the fly image. It's a pitty, because this is not the effect I would like to use.
I'm gonna try to use the layer mask technique described in https://www.youtube.com/watch?v=rP2bnQqLAvI to achieve what I want, but I think that it's gonna be difficult.

[Grimm90]

Combining effects is key
Try putting an "auto mask" effect below your fragment effect .

You could also animate X / Y position of the fly clip for your look.

[smantik]

Thanks. I used AutoMask as you say, but it creates an undesired black edge in the fly. Also, when I move Opacity of Fragment Shake effect, the fly goes to black till it disappear and then the "shaking" flies appear in a black color.
It is strange, because the problem was shown only when I put the background layer with the paper, which has no alpha and fill all the frame. If I use several layers, each of them with one fly with alpha, without using a background layer there is no problem.