Here's the story: My home network has three computers attached to it. One has a wired connection to the router (an Asus RT-N66U), one has a wireless (5GHz) connection, and the last a wireless (2.4GHz) ...
Apologies for a non-trivial edit here, but while I haven't solved the problem yet, I am indeed an idiot and forgot that both of these computers are running Windows 10 (confused one with my work laptop ...