Haven't got one ever but you might try booting from the floppy rather than installing from it - I read on the website the floppy is bootable.
Just to see if it makes a difference, although I am assuming here you have a real floppy drive to boot it with.
If you have things connected to Gayle chips, like CC reset fixes, that might be it.
Or the PCMCIA port connector on one machine is damaged, or perhaps the actual Gayle chip or supporting circuitry. If you are brave enough and dextrous enough to swap Gayle chips, for testing, that might show a hardware fault.
Sounds like you have a problem with one A1200... Unless you are just trying to boot from the PCMCIA port on the "faulty" A1200. You can't boot from the CFC driver supported disks, unlike real PCMCIA flash disks supported by carddisk.device. That is my understanding, take with pinch of salt.
