I am also encountering the same issue. I have the 4GB B01 model with iso sd-blob-b01.img.
It worked fine throughout the week and then all of a sudden yesterday the terminal wouldn’t work and everything locked up. Naturally, I reset the machine and it would lock up at the logo. I kept getting squashfts errors.
I am guessing I either, have the wrong iso image for the Jetson Nano or the 400GB SD card is capoot! There is a way that I’ve been able to bypass the lock up on the logo screen and that’s with pressing and holding Alt + Ctrl + Del where you might have to do it a couple of times.
If anyone has encountered the same issue, this might be a temporary solution to be able to log into the Jetson Nano when it locks up. From what I’ve encountered, it’s going to happen all the time but at least you will be able to access your files or even save them to a usb.
Hope that helps.