I have found that on multiple occasions the Waze mobile app sends me on hairpin turns. That is it sends me in the wrong direction on an intersection, and then requiring a 180° turn (or a set of four 90° turns around a block to get back to the proper direction of travel). In some cases it forces me to go straight on a traffic light, do a 180° later on the road, just to return to the same traffic light (where the turn was allowed anyway).
I have checked the maps myself and all of the roads and intersections seem properly defined, but for some reason Waze keeps sending me on these odd turns. So much so that I have learned to identify them long before it is too late.
I have similarly seen Waze direct someone on the wrong direction in an intersection, just to retake the same direction on the same road that was being travelled. In that particular case I think I identified that the cause is that Waze's 'preferred route' algorithms seem to be interfering with common sense. I have used the same intersection for years, and that 'wrong turn' is what I use when the traffic lights had a specific pattern, which I knew would shave me a couple of minutes, but it was always in a case-by-case basis.