@Harcum 

Hi, is it the main Deco or one of the satellite Deco X20s?

It is suggested to swap the location and power adapter with another Deco X20 to see whether it might be related to the power supply.

If it is the main Deco, please refer to:How to replace the main Deco with another Deco

If it is one of the satellite Deco, you could swap its location with another Deco X20 without extra configuration.

Thank you very much and best regards.