i was failed in the Step 3-4 and got the Error Code: 16.
did i missing any thing? please advice.

0) Initial state: PW3 , 5.8.9.2 set English (US), registered during purchase (around 2015),
Blocked OTA via update.bin.tmp.partial directory in root.
1) Serial G090 G1
2) i try to [reset Device] and connected with Amazon account again.
3-4) Got [update_pw3_5.9.6.1_factory.bin] from another forum.
md5 is the same with yours: a5460e698a531c7770ba2b1ac31667b0
on the airplane mode, i try to update my PW3, after few minuites i got the update error code : 16.
after i reboot PW3, it still can work normally.