If that is true for multiple devices, I would start the return process and have them send you a new one.

Things I would try. Is the router in router mode and connected direct to the modem with a good Ethernet cable. If the modem is a gateway (modem/router combo) be sure the WIFI is off on the modem. Power down any extenders, repeaters, etc. Move the router to different location even if you do it only for a test to check for possible interference and test it. Turn the router off and check to be sure you do not have any SSIDs with the same name. Be sure you are using the power adapter that came with the router. If attached to an UPS, bypass it. Do a factory reset. Update the firmware. If firmware is up to date, reload the firmware. If all that fails, see if you can get them to replace the router. Let us know what happens.