The inconsistencies are caused by the following.
1. The Boltek system: You are dealing with single antenna ranging using signal strength to determine distance. This is very imprecise at best. The software just makes an educated guess at the range.
2. Antenna siting: The location and/or height of the antenna significantly affect detector performance.
3. Antenna alignment: It is very difficult to mechanically align the Boltek antenna so it faces true North. Even with software offset it is very difficult to get it right without a real time reference from a known good source like the NLDN.
4. Calibration: Calibrating ranging is a very tedious and time consuming effort especially with Nexstorm.
5. Site difficulties: Surrounding terrain can play a big part in the overall performance of the system. I have mountains 9 miles to my North. They cause all kinds of anomalies when storms are to the north of the mountains. Local electrical noise can cause headaches. Leaves on nearby trees coming out in the spring can have a significant effect on system operation.
So why install one?
1. If you like to tinker with technology these things are a tinkerer's dream.
2. You can get a good idea of storm strength from the system.
3. They are a good draw for your website. Your lightning pages will be among the top hits for your site.