I'm wondering why mission objectives (things to scan in missions, both on the ground and in space) were removed when you press the V key? Probably so you can just find data samples. But now, sometimes I've been running around a zone for 15 minutes trying to find the last thing to scan.
Sometimes data samples spawn under the terrain and will fool with the scanner. Don't forget, that there is a range to how far away you can be for the scanner to indicate an object in a certain direction, even if it does say there is an anomaly on the map.
Maybe what it is, is it does not count mission objectives the scan for as anomalies anymore. Last night, I was doing a mission on the ground scanning for probes. I got all the data samples and had only one probe left. When I pressed V, it said I had 0 anomalies.
I tried walking past it in one direction, then scanning, then walking past it in the other and scanning, it didn't seem to give me the blue shining trail of where to go to.