I'm not an UEFI dev but a sysadm using UEFI to netboot using PXE/HTTP IPv4/IPv6.
It took a lot of time for me to discover why the firmware was failing
to accept the URL offered by the DHCPv6 server. I only got this pretty
quick message:

"Error: Could not retrieve NBP file size from HTTP server."

I needed to record it using a camera and play it frame by frame to be
able to read it from a real HW. However, that didn't give me a clue
about what was happening. After I read the code (I'm also a dev), I
noticed that many conditions could lead to that same error message. In
my case, it was the server not setting the content-type to
application/efi.

Can't we have better error handling to inform the user what is really wrong?
Can't we have a single second of delay when an error occurs after the
boot process was attempted (i.e. after DHCP answer is good)?