There were a couple of version of the auto-inject floppy (or was that the 800K vs. 1.44MB versions) which required different cables, red stripe vs. yellow stripe. If you use the wrong cable with the floppy drive, it will continuously eject.

My memories on this matter are hazy, but there was definitely a continuously ejecting floppy because of the wrong cable issue back when. If you did not replace your floppy cable, perhaps the drive you installed is of the opposite type from your old floppy drive.