Smart Controller and drone was working perfectly fine for many months.Then, SC got connected to a WiFi and forced me to update, even though there was not enough memory in the SC's internal storage at the time. Windows 10, fully charged SC, internal storage got cleaned up (the entire "Other" folder was moved to an SD card -- DJI's clean up feature was useless), so plenty space.

Tried via the latest (V2.0.12) DJI assist via USB cord, and these are the end results I am getting at various attempts:

• it either gets stuck at whatever percent of uploading
• the SC screen goes black, then starts beeping, then powers off itself
• SC sometimes shows up in DJI assist, sometimes does not, no clue why
• SC's memory as USB storage never shows up in the PC
  

Tried via Wifi

• stuck at updating 1%, and only 10 s pause-power button combo shuts it down
  

Trying to update to: V01.00.700 from V01.00.530. In DJI Assitant, account ino, device info are ON, product improvement prog are OFF, assuming these do not make a difference.

This is an embarassment for DJI and a pain in the *** for costumers.  A simple software update.

Any suggestion? Prefer not to factory reset since, Litchi, OsmoMap, etc. need to reinstalled then.

I am having the exact same issue on my mac.  I'm using the latest version of Assistant (v2.0.14). I have used the DJI USB Cable and also a Sony USB cable.  Same results:  Update is downloaded and transmitted.  The update starts and gets to 16%, then I hear 5 beeps after which it shuts down and does not restart.
UPDATE:  I just discovered that my internal storage is 9.5GB of 11.24 available - this may be the reason for the firmware update failing - I think you need 2GB free minimum.  If it is, there should be an message pop up to tell you that's the case.  Now to find how and what to delete - the file system is very cryptic - OF COURSE