I have no idea whats causing that, you might want to look up how to use the export persona, since it is the best tool to export.
Create an art-board around the scene you want to export. In export persona, in the studio, and go to slices. If the entire scene is there, which it should be, press the checkbox right next to the name of the artboard that you want to export (it should be artboard 1). Editting stuff in export format can't go horribly wrong, its basically direct export on steroids. If you cautious about this, duplicate the designer file and try this method. "Slices" is the term used for selections of layers that you want to export. Creating slices is non-destructive, at all. Press the checkbox next to artboard 1,and that will indicate that you want to export whatever is on artboard 1.
Now, you can edit the properties of the export from the Export Options panel, right above it. You can custom select preferences with the selection tab, or default. If you're exporting JPEG, pick JPEG from the dropdown next to Preset. There are four kinds of export qualities here for JPEG, being best, high, med, and low. That's basically all you need for export persona. When you're done fiddling with other settings for exporting the JPEG if you want, there is a button at the bottom of the Slices Panel in studio saying Export Slices. That will export the selected artboard.
If this doesn't resolve the issue, you might have accidentally added a live filter in the pixel persona. Check out your layers to see if there is a live filter or blend mode (Live filters look like little circles in the layer preview in the layer panel. Blend modes are the drop-downs at the top of the layers panel).