N_Cook said..
clocks presumably related sum and diff fashion with the
crystals 22.579200 and 24.57600 the CLK3 seems to come
from the USB chip with a 12MHz crystal associated
with it, will have to explore the Cypress datasheet

So no luck on the reset? It has stored config somewhere right?
If so it has to have some way of resetting a config then.

I'd still go with a flash but I would be hesitant to do that
without resetting first (if possible).
I've found most resets codes are unpublished.
Try to find out who the service agents were for them as well.

Two more things about the firmware.
If it does allow USB boot recovery (e.g. the firmware fails at some
point in post) it is either going to fix the problem 100% or due
to an underlined hardware problem do nothing.
Hopefully if its truly a proper boot recovery it works before the
code interfaces to the hardware.

I think either way software or a hardware hang flashing it
will not make you worse off if its your only option.