PSP 2018 not saving correctly?

[Wraith_3]

I have an odd problem. I had an image that I used the background eraser on to get only the object in the photo. Afterwards there were artifacts that the background eraser missed. So I went back in and colored out all the unwanted pixels with white so they matched the background. Then save and exit. So I open the picture back up and all the pixels are back. Being a very very very amateur PSP user I thought maybe the format, JPG, was causing it, but it's all along the lines of the object like the background eraser would leave. Any ideas on what could cause this to not save?

[Wraith_3]

I *think* it's the format or resolution of the jpg file. I edited it again and saved it to PNG and it saves what I did.