Help needed with Raid 5 that was working OK

Hi,

My parents had a Netgear RN 104 that stopped working properly, they messed with some settings, messed it up and gave it to me to fix. It has 4 x 4tb drives in Raid 5. I've used mdadm before to recreate a very simple Raid array, so I coected all 4 drives to my computer, installed mdadm and ran
sudo mdadm --assemble --scan
It told me that some devices had the same name. So I went into the config file, 2 were named md0 and two were named md1. So I renumbered them md0-m3 and ran that command again. It gave another error and suggested I use --force which I did, and that got it working, a 12tb volume mounted ok.

I was 20 minutes in to copying photos off when it suddenly stopped, saying I/O error. It could then no longer see the volume. So I restarted, followed all the same steps and now I can't get it to work again. It will show up the 12tb volume but it won't mount it. It says

Error mounting /dev/md127 at /media/ubuntu/7fffffff:data: Command-line `mount -t "btrfs" -o "uhelper=udisks2,nodev,nosuid" "/dev/md127" "/media/ubuntu/7fffffff:data"' exited with non-zero exit status 32: mount: wrong fs type, bad option, bad superblock on /dev/md127,missing codepage or helper program, or other error
In some cases useful info is found in syslog - try dmesg | tail or so (udisks-error-quark, 0).

One thing I noticed was that two of the devices have the same UUID. Could this be an issue? I used the --verbose command and it reported some errors to do with the duplicate UUID, saying it can't decide which one to use, and also saying that one device had failed. I tried switching the drives around, leaving one out, but the one it kept reporting as failed would change, it was not unique to a particular physical drive and was not related to the sata cord.

Can anyone help? Would be massively appreciated, there's a million photos on there.

Thanks!

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