We have 30 pcs of HP z240, i7-7700k 4.2 ghz.
All of them have problems randomly when we reboot or power on.
Sympthoms:
Sometimes when you start the computer, nothing happens. Solution is to turn off and try again, sometimes it starts after one turn off, and sometimes you need to turn it off plenty of times.
Sometimes the same happen when you do a restart. (for example after software install).
Sometimes it stuck before the HP "Sure start" logo, and sometimes its only black.
Very annoying. Have installed the latest BIOS and ME firmware.
Heeeelp!