Well, it's it's complex that it's part of 1000+lines script/solution where I'm buiding a texture map of a bunch of layers. So I was mostly hoping if someone had ran into it before. But I tried to reduce ot bare essentials and got the same effect with linked PSD and script below. So when I run it, all layers but #1 will disappear.
https://www.dropbox.com/s/fxhekp86ctfbp82/translate.psd
var HEIGHT = 5
app.preferences.rulerUnits = Units.PIXELS
var doc = app.activeDocument
for (var i=0; i < doc.artLayers.length; i++) {
var layer = doc.artLayers[i]
doc.activeLayer = layer
doc.resizeCanvas (doc.width, doc.height + HEIGHT, AnchorPosition.BOTTOMCENTER)
layer.translate(0, -HEIGHT)
}