Kunix Quote P.S.
I've just discovered that nuvi 13xx is able to flash RGNs with no boot.bin inside. That means that the bootloader is able to flash regions. For two years I was sure it's impossible. Life is a wonderful thing. Kunix Unquote

I've often thought about this but would not know how to try it.
So in theory you could flash a new image to repair the internal flash drive or any other region which may have become corrupt (Except if the corruption is in the boot block and the nuvi cannot enter into pre-boot mode)
How would one go about making the rgn file ?