White line artifacts when exporting as a bitmap

[Ampa]

Seeing an odd issue with Xara 5 when exporting my image as a bitmap. Artifacts, in the form of horizontal white lines, with a width of 1 pixel, randomly positioned, ofvarious lengths, are appearing in the image.

Makes no difference whether I export as PNG, TIFF or BMP. Changing the antialiasing, on or off in the export dialog, does nothing to help. Nor does exporting with or without alpha.

Anyone else seen this behaviour?

What can I try to alleviate it?

[Searched the forum for artifact / white lines and found nothing]