I am a retired airplane inspector and 99.999% of the time, we used to troubleshoot items that often would NOT present any problems, but sometimes a complicated and truly unique problem would take SEVERAL shifts, even SEVERAL DAYS to troubleshoot. Replace this, replace that, retest, change configurations, replace something different, etc. Nose vs grindstone.
More than once, after replacing a DOZEN components and having the problem PERSIST, we would scratch our heads. I am being serious here, as modern airplanes have very sophisticated systems and nearly all of the important systems are interfaced.
Once in a blue moon, the problem would DISAPPEAR and we could NOT replicate it NO MATTER how hard we tried. When this happened, it was referred to as "PFM." Pure f______ magic. Another more civil "anwer" was "GDA", or "gremlins departed area."
We would dutifully record the parts we replaced, the retests we ran, and get things signed off.
SO----it looks like the DCA you witnessed had some PFM involved. I am convinced that mankind won't REALLY understand how the bees do their thing, and I am pefectly happy to simply watch! (har har har)