A "proof of concept" project was part of a big government IT bid process. To stress the comms network the customer employed a consultant who brought a terminal protocol emulator load generator made from many microprocessors.
In one crucial test their consultant declared we had failed. He pointed to the stand-alone network monitor that apparently showed a corrupt transmission from our system. I looked at it - and pointed out that the monitor had shifted the bits by one place. If you looked at bit level you could see the poll was valid and the emulator had responded correctly.
To prove the point I showed him how to write the displayed hex values as bits on a sheet of paper - then regroup them into octets one bit shifted. It took him a while to grasp the principle - particularly of sending an octet's LS bit first. He apparently knew nothing about the bit level of comms protocols.
On another occasion we were failed for not always seeing responses. We showed him on the monitor that it was his emulator not replying - presumably as it had reached its throughput capacity well short of the test's intended maximum traffic.
I earned my pay on that project.