PW4 MY Kpw4's FW revert to 5.10.1.3 from 5.12.2

I don't know if it is a special case or not，but I think sharing it is beneficial.Maybe，someone will learn something from it.

I JailBreaked your KPW4 using Factory JailBreak (Factory FW) from here.
https://www.mobileread.com/forums/sh...&postcount=455

But Updata fireware to 5.12.2, my Kpw4 lost JB，the";log mrp" do not work.
Before Updata，I flashed the newest ‘hotfix’ （2019-Oct-11 23:23:06）using '；log mrpi'. After the operation, I found out that it is a wrong operation. the ';log mrpi' has't work. But I can still perform the correct operation.
I flashed the newest ‘hotfix’ （2019-Oct-11 23:23:06）using "Update Your Kindle" to my kpw4. it work，but ";log mrpi" still don't work.Finally I put Factory JailBreak (Factory FW) in my kpw4 and update。After reboot，My kpw4's FW revert to 5.10.1.3，and '；log mrpi' work.