Tried numerous times to update firmware from 5.2.7 to 5.2.10 and it keeps failing with error code 12, tried a few of the suggested fixes and cannot get it to work. Help please? 
Please install first 5.2.9
Still get the same error?
I also tried going to 5.2.8.3359 as well, same error 12,
then tried 5.2.8.3332, this time I get an error in the log of FW999
Hello,
witch QTS version is installed on yor NAS ?
5.2.7.3297
Error code 12 usually indicates that the firmware update file was not downloaded completely, or that there isn’t enough system space. Could you try rebooting, confirming that you have sufficient space, and then attempting the installation again? It would also be worth checking the health status of your drives.
Also, could you provide a full screenshot of the failure screen? Thanks!
It does not matter, I have tried the update straight after a clean reboot, I still get the same error
maybe you can try this, using a temp space
https://www.qnap.com/en-us/how-to/faq/article/manually-updating-the-firmware