Once worked an issue on a C5 galaxy written up as “aircraft porpoises while transmitting on HF radio.”
What could the radio have to do with a control system?
Months later, it was determined that the HF radio’s antenna position and frequency interfered with the electrical signals used by the autopilot. So when the pilot transmitted with autopilot enabled, it caused the plane to pitch up, correct itself, pitch up, correct itself, over and over.
Aircraft are incredibly complex these days.
A couple years ago jeep had to “quietly” recall all their new Grand Cherokees because computers kept acting weird, like suddenly dying or accelerating uncontrollably. After researching it they found the cause.
They had started using a new compound that year for the windshield wiper blades. Turns out that if you accidentally turned on the wipers while the windshield was dry this compound somehow produced enough static to cause havoc with the computer.