I dont see much in odd about those results.
Even with static nodes and antennas you can see RSSI variations of 2dBm perhaps 3dBm. If the node is moving along a street (a car say) then signal strength variations of 10dBm over a couple of metres are again not unusual due to the impact of changing reflections etc.
Now consider what these variations men for a node that is 1km from a gateway. A +2dBm change in RSSI means the node has apparently moved position by 400m. A +10dBm chage in RSSI means the node has apparently moved postion by 3km.
And perhaps dont run a node sending a packet every 20 seconds for very long, you can breach the fair use limit fairly quickly, about 20 minutes at SF10 BW125.