RBR50 Attached Device has 2 ip addresses

Have RBR50 with one satellite.  I have a smart thermostat (Ecobee) that I attached to the network with no trouble.  The assigned ip address was typical, 10.0.0.(last assigned address + 1).  Some months later I noticed that a second ip address was assigned to the same device, in the range of 169.254.77.yyy.  I have no idea why, this has not happened with any other attached device.  I also have a second thermostat, exactly the same model, both bought at the same time.  The only difference is, because of location, the satellite may have the signal of the one with two ip addresses, and the other thermostat likely links directly to the router.  Is this a problem?  Why did this happen?  Can I just dump the 169 address?  Should I just reinstall?  Comments welcome!  Thank you!