As a purveyor of floppy disk technology including MFM copiers, SCSI FDs, PS/2 FDs, and NOS ED disks and FDs, I can say that floppies suck and should be assumed to be bad and that any success of reading/writing/formatting is indeed a miracle. Any reading or writing of them will surely lead to their failure soon. And, they will fail just sitting there too.
Back in the day, I did try inducing errors into 3.5" HD floppies by waving a cheap, small voice-coil speaker magnet over a floppy and comparing its contents sector-by-sector to a disk image stored previously. I was only able to do this after opening the shutter and touching the magnet directly to the diskette surface.
PSA: Never write to 5.25" 360K floppies using 1.2M drives because the created track width is too small to be picked up by 360K drives.
Back in the day, I did try inducing errors into 3.5" HD floppies by waving a cheap, small voice-coil speaker magnet over a floppy and comparing its contents sector-by-sector to a disk image stored previously. I was only able to do this after opening the shutter and touching the magnet directly to the diskette surface.
PSA: Never write to 5.25" 360K floppies using 1.2M drives because the created track width is too small to be picked up by 360K drives.