Could be that your cache partition needs a clean-up or something like that...
Anyways, not worth the hassle, just flash the rom you like via twrp, done
Thats the latest one:
Code:
https://d1s31zyz7dcc2d.cloudfront.net/6b45be2a4aa689df55f69967eb67e2f2/update-kindle-full_tank-288.6.7.8_user_678752620.bin
Just flash a fireOS stock rom, wipe data and cache if you come from lineageOS, done.
Code:
5.2.8.7
https://d1s31zyz7dcc2d.cloudfront.net/8e9503fd5cc84475da2be18944ce0246/update-kindle-full_tank-288.6.7.4_user_674730620.bin
5.2.8.8
https://d1s31zyz7dcc2d.cloudfront.net/bc7bad4c0b5d7300fc27f8b7f57104a5/update-kindle-full_tank-288.6.7.6_user_676742620.bin
5.2.8.9
https://d1s31zyz7dcc2d.cloudfront.net/6b45be2a4aa689df55f69967eb67e2f2/update-kindle-full_tank-288.6.7.8_user_678752620.bin
If you like to unroot and to lock the bootloader too, wipe data is necessary, then flash the boot.img (out of the .bin update you flashed in the first place) via hacked fastboot...