Pi2 bootcode.bin puzzle

Twice now a Paspberry Pi 2 v1.1  using the bootcode.bin-only
method to boot from usb mass storage has abruptly
stopped finding the mass storage device, or so it seems.

The machines are actually running freebsd, but the failures
are seemingly too early in the boot process to get anywhere
close to freebsd files.

In both cases, the failures occurred "out of the blue" during
a normal reboot with no change to the system. I've monitored
power supply voltage during boot, it stays above 5.2 volts,
measured via one of the usb ports, on both powered hub and Pi2.

Here's a transcript:



Raspberry Pi Bootcode

Found SD card, config.txt = 0, start.elf = 0, recovery.elf = 0, timeout = 0
Trying USB
Set address 4
Num devices = 1, addr = 4
get_config_descriptor 41 bytes
Initialise hub
Found 5 ports, multi_tt = 1
Setting interface 0
Enabling PORT POWER on port 1
Enabling PORT POWER on port 2
Enabling PORT POWER on port 3
Enabling PORT POWER on port 4
Enabling PORT POWER on port 5
Waiting for devices to respond to reset
Found device on port 1
Found highspeed device
Set address 5
Num devices = 2, addr = 5
get_config_descriptor 39 bytes
device class = 255
Device found: type = Ethernet adapter, addr = 5
Found device on port 3
Found highspeed device
Set address 6
Num devices = 3, addr = 6
get_config_descriptor 41 bytes
device class = 9
Hub device found at addr 6, enumerating HUB
Initialise hub
Found 4 ports, multi_tt = 1
Setting interface 0
Enabling PORT POWER on port 1
Enabling PORT POWER on port 2
Enabling PORT POWER on port 3
Enabling PORT POWER on port 4
Waiting for devices to respond to reset
Found device on port 3
Ignoring low speed device
Found device on port 2
Ignoring low speed device
Found device on port 4
Ignoring low speed device
Found device on port 4
Device failed to respond to reset
Trying booting from Ethernet device addr 5

At this point the Pi goes into a netboot loop. It doesn't seem to
activate the disk drive apart from one blink of the activity LED.

The Pi still boots from a Bookworm microSD, so
it doesn't look like a broken Pi2. I've been
using the version of bootcode.bin linked at
https://github.com/raspberrypi/firmware/blob/master/boot/bootcode.bin
from the page at
https://www.raspberrypi.com/documentation/computers/raspberry-pi.html#raspberry-
pi-boot-modes
but didn't change anything betwen working and not.

I notice that the narrative at that page is somewhat tangled.

In one, and so far only one, instance the Pi booted sucessfully
during a sequence of tests while makeing and re-making USB connections.
That led me to suspect a loose plug, but multiple repetitions, moving
all plugs, didn't repeat the success.
 
Can bootcode.bin pick up any parameters (other than noting the
presence of a timeout file) from any files placed on the microSD?

Thanks for reading,

bob prohaska