This can cause real problems. Usually it is caused by one or more devices using a static IP address that conflicts with either another static IP or one dynamically assigned.
If two devices are both static and conflict, one needs to be reconfigured.
If a device is using a static IP that conflicts with a dynamic one, then one of the following is usually the cause:
- The device’s static IP is for a different location. Change the location to one that matches the local network, like “Automatic”. This is especially important for Macs. Not so much for iOS devices, since their location is determined by the Wi-Fi SSID.
- The device’s static IP was taken from the range of addresses that the local DHCP server (usually a router) is using for dynamic addresses. Change the static address to be outside this range or reconfigure the router to change the range.
If your device has a dynamic address and is still in conflict with another device, then there may be a bigger problem (like a bug in the DHCP server, in your case), because DHCP is supposed to detect this situation and request a new address when it happens.