Even top of the range smartphones have fairly basic GPS chips. What this means is that the GPS accuracy of your current position can be imprecise, and constantly recalibrating. When your device thinks you are in a different position (even if you actually aren't) then the 3 word address will update.
This can also mean that multiple devices very close to each other might show different 3 word addresses, not because the 3 word addresses of your actual location is different but because the devices each think they are in slightly different places. Our app converts the GPS location into a 3 word address.
If your device isn't giving you a stable current location, then try moving the map so that the pin is in exactly the position that you want on the map/satellite image, rather than relying on the device's GPS accuracy.