After checking the SVG, the construction is a bit of a mess TBH. It contains both raster and vector elements with the raster images contained within clipping paths. These seem to be creating conflation artefacts around the clipped raster images, i.e. where the solid areas meet the transparency. It's a bit weird though to be honest. I wouldn't have expected that. Might be Windows Photo viewer to blame. It's not good with transparency.
One possible fix is to create a white filled rectangle the same size as the page.
Enable the page borders in the Document settings.
Use snapping to page border to get it the rectangle to fit exactly.
With the white rectangle selected press End or do Object > Lower to Bottom. Basically this will create a white background behind everything.
Finally in the Export dialog use the "Page" option for exporting.
Here's an example PNG output using that technique, looks good.