Reminds me of a funny incident years ago. Airplane was a 748 and engineer did retraction tests in hangar then taxied airplane to line for me to fly. He came into the ramp (engineers could taxi under power there) taxiing fast and rough, and abruptly spun around and went back to hangar. I called and he said the nosewhel steering was inop, needed a new valve. None available, would be AOG.
Small island, and nothing came in for about 5 days, but then the airplane appeared on the ramp, serviceable for flight. I asked how he fixed it and he said he used an old valve that he repaired. (he lied of course)
Later I discovered he had left the gear handle up after the retract test on jacks, and when he taxied there was no pressure in the down line, where the steering gets it power.
If he had not had the pins fitted, we would not have had that airplane back for quite a while!