For older "pre-HEOS" models like the X4000, you may need to contact Denon Product Support
For weeks, the X4000 had been glitching. The Network Audio standby light would blink erratically, and the GUI would freeze whenever he switched from Blu-ray to Spotify. The forums—the dusty, forgotten corners of AVSForum and Hi-Fi discussion boards—were unanimous. It was a firmware corruption. He needed a fresh install of the firmware update file. denon avr x4000 firmware update upd