Well that flash layout and file system type is different from what I've seen on a 7816N-E2, on which I've used 7616NI firmware. So I'm not able to speak from direct experience of your specific model.
What I'd suggest is grabbing a copy of the listed mtdblocks as a current state backup.
An easy way to do this - if you have a handy network share - is to use the 'storage menu' (I'm assuming this older firmware has one) to define a NAS destination. It doesn't need to be formatted.
If you can do this, the path will show with the mount command. Lets says it's /mnt/nfs00
So:
cd /mnt/nfs00
umount /dev/mtdblock1
cat /dev/mtdblock1 > mtdblock1_save
mount /dev/mtdblock1 /home/hik
cat /dev/mtdblock0 > mtdblock0_save
Hopefully the re-mount won't give an error.
This Hik download site has a rich choice of firmware which appears to be for your model.
http://www.hikvisioneurope.com/port... Firmware/Recorder/DS-7600NI-SE 7600NI-V(VP)/
So far, I've not seen any stability or reliability issues of any consequence with the NVR firmware I've tried.
But they have been different from yours.
On the 7816N, the firmware is just a simple cramfs image (with a header) which is copied straight on to mtdblock2.
Looking at the 3.0.15 version from the site above, it looks like it just holds the 17 files as below:
File 0 webs.tar.gz filelen=48 filepos=812 checksum=5811
File 1 app.tar.gz filelen=216 filepos=860 checksum=26213
File 2 hicore.tar.gz filelen=696 filepos=1076 checksum=89135
File 3 ntfs-3g filelen=16 filepos=1772 checksum=2049
File 4 vps_logo.bin filelen=16 filepos=1788 checksum=1867
File 5 log.tar.gz filelen=16 filepos=1804 checksum=1995
File 6 player.bin filelen=16 filepos=1820 checksum=1995
File 7 hicore.tar.lzma filelen=4549864 filepos=1836 checksum=580198167
File 8 8107.tar.lzma filelen=800984 filepos=4551700 checksum=102113057
File 9 versionctr.tar.lzma filelen=659568 filepos=5352684 checksum=84015264
File 10 app.tar.lzma filelen=1662312 filepos=6012252 checksum=211858922
File 11 dvrCmd.tar.gz filelen=12432 filepos=7674564 checksum=1596911
File 12 uImage filelen=1952200 filepos=7686996 checksum=248780104
File 13 rootfs.img filelen=509408 filepos=9639196 checksum=65049899
File 14 webs.tar.lzma filelen=3622536 filepos=10148604 checksum=461883850
File 15 start.sh filelen=2048 filepos=13771140 checksum=268495
File 16 new_10.bin filelen=1320 filepos=13773188 checksum=184118
If you can compare that file list with the running contents of your /home/hik and there is a good match, it may be that a copy of mtdblock1 would be an effective backup of the as-is state of your NVR firmware.
You might also want to take a peek with a Hex editor (eg HxD) at the 'hardware descriptor block' in mtdblock0 (starts with the Hik magic number of SWKH) to see if your language=1 is real, or the product of seller-modified firmware.
The byte is likely to be that at 0x10 relative to the start of SWKH in the hardware descriptor block.
But - here is a warning - sensible advice would be 'if it's not broke, don't fix it'.
You will no doubt have read loads of posts here in this forum of Hikvision owners doing what should be a natural and reasonably safe firmware update, to get bugfixes, security fixes, new functionality etc - but suffering adverse consequences. There is definite risk with attempting firmware updates. I haven't done it to my 'production' NVR, just the one I bought to play with. Though I have done it on cameras, where a bad result even if only temporary has less of a consequence.
PS I don't think your firmware link is correct for your model. The suffixes are confusing and significant. Maybe others with your model can comment.