I'm testing PEMPro v3 here as well just using the sims through SGP. I also see the same behavior but it looks like SGP is reporting that the image is complete and returning as such when requested. It then looks like PEMPro deletes the image at some point. I can't tell what happens between those two points in PEMPro but SGP doesn't delete images (it will just keep increment the file name) so something besides SGP is removing the image.
You can see this happening by monitoring your PEMPro folder:
C:\Users\Jared\Documents\CCDWare\PEMProV3
Looks like it's doing something with a PaLightFrame.fit and a SGProImage.fit. I see both of these getting created and deleted but the graph doesn't move.
Thanks,
Jared