Why is my printer ticking? [solved]

Ever since I hooked my printer up to the Ethernet (over a patch panel), it makes a ticking sound exactly every three seconds.

Before, it was connected via Ethernet cable to a Raspberry Pi that served as WiFi adapter, and that setup didn't tick.

Update: The ticking stopped after deactivating DHCP. It's a Kyocera Ecosys M5526cdn.