Hacks Paperwhite 7th gen (PW3), jailbroken, stuck in a loop on the Kindle logo after a KORe

[Art15]

Hi all, I'd appreciate help recovering my Kindle.

Device: Kindle Paperwhite 7th generation (2015)

Jailbreak method: Winterbreak, completed in August
KOReader version: Latest
Other hacks installed: KUAL


What happened:
1. Jailbroken, KOReader working.
2. I copied a custom KOReader plugin (a Lua map plugin, "OldKindleMaps") into koreader/plugins/. It was written by an AI assistant and had NEVER been tested on a real device.
3. The plugin worked briefly, then crashed. When I opened its online mode, KOReader exited or the whole Kindle restarted.
4. Since then the Kindle has been stuck on the Kindle logo.

Current symptoms:
- Shows the Kindle logo and nothing else.
- On the charger the light is solid amber.
- If I hold the power button long enough the light blinks amber, and sometimes the screen flashes white and black, then returns to the logo. So it seems to restart but never gets past the logo.
- I let the battery drain and have charged it on a wall adapter for 2 hours.
- Access to the storage: it does not appear as a drive when connected to a computer.

Questions:
- Is this a known boot loop on the PW3 after a jailbreak or a KOReader crash, and what usually causes it?
- Is there a way to recover it without a full factory reset, or at least without losing everything?
- Could a plugin in koreader/plugins, or a large map file, cause this, or is it more likely the jailbreak or firmware?
- If it can't be recovered at home, how should I handle Amazon support, given the device was jailbroken?

Thanks. I can post more details or the plugin files if they help.