It turns out I was playing Don Quijote when I was trying to fix the reset issues I had with my slug.
Of course, I was suspecting the USB rack for the issues, but the issues never showed up on the laptop... until now.
I decied to temporary use a USB stick for the FS and started copying files over to the stick. During the copying the rack disconnected and everything became more clear. I was tilting at the windmills all the time.
BTW, be smarter than myself and just change the UUID to mach the old one instead of regenerating the initrd and reflashing it:
tune2fs -U the_uuid_of_the_previous_root_partition /dev/sda1
Oh, next on the agenda will be to use my ipod mini as a hdd for the slug in order to prevent ruining the stick... And another thing, total silence is really nice, even if the rack was not that noisy.