looking for a way to animate 16 png files, crop too, swiftly in Xara designer

[Egg Bramhill]

First & formost your screen grabs are not exactly the same alignment. This is an issue outside Xara.
All the screen grab images in your file is 2560 x 1080 px.
Utilites / Options / Page Size / set to 2560x1080.
With the view-all and select all open on the Action Frame Gallery, Select All.
Set the origin point to Top Left.
Set the 16 selected images to 2560x1080px
Export animation.
It works but it's too big 2088Kbs and because your screen-grabs wheren't exactly aligned (or perhaps your method of cropping) there's a slight jump in the animation.

I reset the page size to 1280x540 and reset the 16 images to the same.
This created an animated gif of 636Kb which is probably still too large but it could be reduced further using backgrounds and overlays.

Heres the animation after painstaking re-alignment, this one set to 800 x 428 (289Kb)
I would know the value of such a gif unless it was for software promotion, neither would I do this animation as a gif.