Operating complex equipment out of spec can cause strange malfunctions.
There was a (non fatal) crash of a A320 that was being used for training a few years back (Flight 9001), there were doing touch and goes, normally when the wheels contact the runway a pressure sensor tells the computers to enter landing mode.
But this is undesirable during touch and goes so pilots use the manual controls to override the computer, when the manual controls are being used a rod presses down a microswitch to tell the computer that is is being overridden.
What the pilots didn't know is that the wrong lubricate had been used on this rod, so it was not making contact with the microswitch, this meant the ELAC flight computer that controls the elevators thought that it was having a malfunction and shut down lettings it's redundant twin take over.
A single ELAC failure is not considered urgent so the warning will not show during takeoff or landing in order to not distract the pilot.
On the next touch and go the other computer also thought it was malfunctioning and also shut down, when both elevator control computers are offline control of the elevators is handed over to a different set of flight computers called the SEC.
But exactly as this happened the plane bounced off the runway, the two SEC computers poll the landing gear sensors every 120 miliseconds to check if the plane is on the ground, but they are not synchronised, one polled the sensors and decided that the plane was on the ground and the other detected that the plane was in the air both imminently detected that discrepancy and declared a fault and both shut off.
This left the plane in the air with no running flight computers capable of controlling the elevators or horizontal stabilisers, a warning sounded that use manual pitch trim only, the plane hit the runway hard with both engines striking the runway before the plane went airborne again, the impact caused the flaps to malfunction and both engines to catch fire. The safety pilot observing eventually figured out what was going on and took over pulled out of a 2.4G dive and managed to land the plane after doing a go around.
A tiny deviation from spec can cause massive faults, modern aircraft are only as safe as they are during to the maintenance standards and tight specifications and protocols.