4036's U-Boot systex is very unique.
If you want set up some parameter don't use "="
If you setup server ip you must type below.
server ip 192.168.0.1
(NOT server ip = 192.168.0.1)
If you use "=" that mean delete that parameter.
That's all.
And may I have a question?
This is my firmware upgrade test screenshot.
Why your upgrade file name is upgrade.tgz?
Normally upgrade_all.tgz has all firmware and software.