"It was found that the contaminated swabs all came from the same factory, which employs several Eastern European women who fit the type the DNA was assumed to match. Bavaria, although a region central to the crimes, obtained their swabs from a different factory. They had no reports of crimes committed by the Phantom."
The cause for all DNA detections was: the use of sterile but not DNA-free cotton swabs:
"the laboratory results were due to contamination of the cotton buds used for DNA probing. Although sterile, the swabs are not certified for human DNA collection."
The Wikipedia article lists the locations of the crimes, obviously these swabs were more widely used, and they even weren't used in Bavaria.
Well, I could google some examples for you but I spare you the details. I worked for/with the police and the military in the US. Trust me, I know what I am talking about. One look at them is enough for me. (Yet, the German Army and the BKA know what they are talking about).
It was obvious that this was an artifact. I mentioned this long time before the case was "solved". https://www.metafilter.com/73462/Onewoman-crime-spree
What is the biggest achievement of the Bavarian police? Being so incompetent in the 72 olympics so that the GSG9 special forces were created.