There are many regions [rgns] potentially available in garmin units' non-volatile memory, but nowhere near all are used on any one particular device. The most crucial of the regions is rgn41 because of the unit specific data it contains, and this is the region that is referred to when we talk about 'doing an NV Backup'. Some other regions also contain 'personal' data, but many don't. An example of the latter is rgn16 which contains the logo/splash, usually the same rgn16 will be common to all units with the same HWID [although, for example, in 1xxx various logo bins 'versions' do also enable/disable features].

You've already found out [twice] Carlos how crucial region 41 is to restore your 3790 when it decides to become a 37xx. Do it regularly, at least with every fw update as dasilvarsa said. I try to go even further and back up the entire NV ... i don't always do it, maybe every second or third fw update with just 41 in between. If you'd like to do a complete NV dump of your 3790, here's the kit:
[Only registered and activated users can see links. ].
Just unrar it to a clean microSD, insert it with your 3790 fully off [press and hold the on button until you get the prompt], turn it back on, check 'Loader' is displayed and go make a coffee. It takes quite a bit longer than backing up just rgn41 so make sure your battery has enough charge. The file 'ldr.bin' is just the boot.bin of the current v5.00 fw, so make sure you update it when the fw version changes on the unit.