I know. This forum takes a bit of getting used to... :P

ExifTool can now be used to edit the X/Y resolutions stored in the JFIF segment. It won't write the JFIF segment if it didn't previously exist.

Adding the JFIF information back in would be a fairly easy thing to do, but I don't think this will solve your problem because any image editor should be able to open a standard (non-JFIF) JPEG image. All of mine do. So it must be more than the JFIF information that is stripped off by your AP software.