is there any room left for not being able to explain odd happenings?
Yes, the flip side of high tech detection is high tech concealment.
Criminals can know all the tricks used for detection, and have their own high tech to conceal what they've done, or mislead the high tech equipment, or fake the high tech evidence. Or use exactly the same high tech as the detectives to make sure they leave nothing behind.
For example, long ago, I worked a gig in bank financial security. (I was a high tech consultant). Remember when credit cards introduced holograms on cards as a way to prove they were authentic? That was done in response to organized crime simply manufacturing valid credit cards, instead of stealing them. They had the machines, plastic, etc to just create a forgery of your card, and buy some stuff with it that they then sold on the black market, like cigarettes or jewelery. They got the names and numbers from waiters and store clerks; remember those carbon impression receipts they used to keep? They just paid some shady servants for copies of those. (In modern times, an iPhone could snap a photo of the front and back of your card). The holograms couldn't be easily faked!
But about a year after the introduction of holograms; some criminals hijacked and stole an 18-wheeler carrying a credit card printing machine for these hologram cards, along with raw materials to print tens of thousands of them.
You don't have to duplicate the holograms, you can just steal them. They never got caught, and presumably the rest of the operation continued as before (and may still continue).
Technological detection and concealment are in an arms race, every advance in one prompts an advance in the other. Exploit that and you can create mysteries and events nobody can explain.
Of course your other means of accomplishing this are magic, aliens, time travelers and antiquity. DNA and other biological evidence can degrade very quickly; especially trace evidence if somebody was aiming to be careful. And concealment 101 still works, satellites don't see through stone or steel barriers, and people (esp criminals) can communicate in codes that only they know.