I've upgraded to 5.4.3 from whatever it was (pre 5.4.0 for sure) without any issues.
Also i wouldn't recommend updating via WIFI so grab a cable, update firmware and only then configure wifi.
Had it for a day on WIFI and wasn't happy with performance so just left it on cable.
Yes - he's no expert, or Yes - it works ?? just kidding :D
Found your other post regarding this cam and ordered one (still way cheaper than HK cube).
1080P HD High Definition Video Resolution IP Camera Online Shopping| annkesecurity.com