I tried to create a backup of rgn 41 of my nüvi 66LMT but failed, yet the update.log states that the process was successful:

nüvi x5 Software Version 2.20, UID: xxxxxxxxxx, HWID: xxxxxxxxxx
------------------------------------------------------------------------------
Parsing "rrgn,41,1:/41.bin"
Success
Parsing "reboot"
Instead of a 41.bin file, I get a last_id.bin file with a size of 1 KB only.

I used Nuvi65&66_220.gcd to create the Ldr.bin file. I am aware FW version 2.70 has been released, but I thought I'd make a backup using the currently loaded version first before updating (the unit is still in the same condition as when received).