Shiftee uses a public IP address of your router. Most of the cases, a public IP address is static(fixed) and will not change unless you power off the router. Therefore, your assumption that your WiFi IP is dynamic could come from the private IP address assigned to your smartphone devices. Shiftee do not use the private IP address that is assigned to each device.
If you happen to turn off your WiFi router then power back on, the public IP address might have been changed. Then, one of Supervisor, Manager, or Owner has to re-register the WiFi IP address of the location. However, this is very unlikely as long as the WiFi router runs 24/7.
For more information, please refer to Timeclock Area and WiFi