Technicolor router problem?

Hi recently supplied with Technicolor dgn2231 router when I attached my WD elements 2tb hard drive, all was good until the router restarted itself, which it then did every hour and continued to do. I’ve now put my old zyxel router back and the WD drive works as well as it did before. Despite looking everywhere cannot work out why the Technicolor is not compatible. Both Technicolor and my isp (kcom) totally useless! Any suggestions?