Banding on exported PNG (XP5)

[stratocast]

Here's something I came across recently. I've been away from the forum for a bit, so apologies if it has been covered before.

I was making a basic gradient PNG image for a web page background in Xtreme Pro 5 and the exported result had banding left and bottom. A bitmap copy made in Xtreme also had the banding. This appears only to happen with gradients.

I switched to Xtreme Pro 4 and it exported perfectly.

Anyone else seen this?

(Sorry about the quality of the attachment, it's a GIF)