Region 5 is written by boot.bin (ldr.bin), when it's executed on the device.
Usually Garmin devices don't boot dues to corrupted contents in regions 41 and 48.
Now, when you can flash region 14, try erasing region 41 with ergn,41.
Then try entering the mass storage mode with QuickCure3 or GarminCure3 (fw_all.bin-only firmware, of course).
If it works, format the internal drive with RMPREPUSB.
Region 48 most probably can be flashed with boot.bin-less RGN. But you need a few first megabytes of a correct filesystem dump.
Region 41 most probably can't be flashed with boot.bin-less RGN. Both bootloader and boot.bin disallow this.
We can patch boot.bin, but if ergn,41 won't work, that means, boot.bin can't write region 41, and therefore you can't change it.