Kindle Oasis (10th) boot loop?

[erk]

I got a "Certified Refurbished" Oasis 10th/2019 that crashed into a boot-loop.

Does this model have an accessible serial port (I have ttl serial hardware), that I can mess with fastboot and restore a factory image?

Any options to actually fix this - the USB device seems to show *very briefly* sometimes.

[j.p.s]

No serial port has been found yet and there have been no reports of being able to nodestructively open the case.

[erk]

What in the early boot chain exposes the 'usbms' device?
Is this uboot ?

This is a KOA3. It fails to completely boot (reboots during tree screen).

Once the battery drains, and it is at the "Low battery" display
-- so no Linux kernel running for the gadget driver?

usb 1-2: new high-speed USB device number 42 using xhci_hcd
usb 1-2: New USB device found, idVendor=1949, idProduct=0004, bcdDevice= 4.01
usb 1-2: New USB device strings: Mfr=0, Product=4, SerialNumber=5
usb 1-2: Product: Internal Storage
usb 1-2: SerialNumber: G000WLXXXXXXXXXX
usb-storage 1-2:1.0: USB Mass Storage device detected
usb-storage 1-2:1.0: Quirks match for vid 1949 pid 0004: 80000000
scsi host2: usb-storage 1-2:1.0
scsi 2:0:0:0: Direct-Access     Kindle   Internal Storage 0401 PQ: 0 ANSI: 2
sd 2:0:0:0: Attached scsi generic sg0 type 0
sd 2:0:0:0: Power-on or device reset occurred
sd 2:0:0:0: [sda] Attached SCSI removable disk

This is particularly strange because WITHOUT seeing the 'low battery' message on screen, there are two options.

1. "1949 : DEAD", HID when it is at low charge
2. absolutely NOTHING - no USBMS gadget at all.

However, released u-boot binaries don't have the "Internal Storage" string - so where is that coming from???