I am in the same boat as you my friend.
PW4 with FW 5.16.8
Multiple tries using Winterbreak v1.7.0, v1.6.0, and v1.4.0
Loading files on root including hidden files before registering device.
Registering as fast as possible to turn on airplane mode.
Soon as it tries to load the store the wifi flickers and gets unexpected error.
Have tried with and without deleting update.bin.tmp.partial that gets generated as soon as device is registered.
Have factory reset multiple times with DO_FACTORY_RESET and repeated the process to no avail.
Have read 47 pages of forum replies here
https://www.mobileread.com/forums/sh...73#post4505673
Haven't tried finding a update >5.16.8 and <5.18.1 and manually updating FW and trying again.