You’ll need to get a boot log up until failure, which you can do with a serial console. See:
Unfortunately, since it locks you out so quickly, there probably isn’t another means of getting the log. Even if there were another means of doing so serial console would still be the method of choice since it can log the boot and since serial console logs even during bootloader stages prior to the Linux kernel ever loading.
One test you might try, which would be simple, is to see if it still fails if nothing is plugged in to USB during boot…if you plug in USB after boot results may change. Or if you unplug and replug USB after the failure. Having ssh fail though tends to say the only way you will get required information is via serial console.