@lucasrato,
To be safe, don't install 5.12.x just yet. It might have new measures to force auto-updates, as was discussed on this forum earlier.
You can install customer firmware like 5.11.x (from Amazon Update page for your Kindle) and then immediately apply JB Hotfix, reinstall all packages and you are good to go.
(Essentially, you needed to install a customer firmware before you install KUAL, etc)
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