Signal reception can slightly change over time. If a base station receives a message with a poor RSSI (e.g. -140 dBm) it might not receive next messages from the same device. In such case, the Network Location position can vary significantly.
Let us take the following example:
A first message is sent by a static device.
The message is received by 2 base stations: BSA at -140 dBm, BSB at -137 dBm.
A second message is sent by the same device, still static.
This 2nd message is received only by BSB at -141 dBm.
The 2 base stations are 20 km apart.
Then the position of the 1st and the 2nd message will be several kilometer apart.