This is something that is not possible in our configuration. The device running the TFTP server is a data at rest module, with all boot images and files to be located on an encrypted drive that gets mounted to it (/rmc0). Therefore, the server directory has to be located on the drive.
@linuxdev to follow on, using tcpdump, I was able to trace the download to start timing out at the same block of the boot.img file each time (block 15973).
I am curious if you could set up a fully/normally booted Jetson to perform a simple TFTP download of that image? This is not for boot, this is just to test if there is a bug related specifically to downloading that file using boot software versus a bug in general, and if a normally booted Jetson hits an issue at that offset, then the problem is different than if a regular running Jetson can successfully TFTP download that file.