When only one other house member is dreaming and on your plane, it appears to be reporting the incorrect room.
In the example below, Gleali and kirtes omathear were both in Provenance (Threshold), reported correctly on Locate Dreamer, but House Members reported them in rooms they left some time ago.
House Members borrows a lot of the message handling directly from Locate Dreamer, if I recall correctly. However, it seems to be reporting the wrong room.21:27:47: You begin evoking Locate Dreamer
21:27:47: Gleali is currently in Provenance, in Threshold, Gateway to the Dream City
21:27:53: You begin evoking Locate Dreamer
21:27:58: kirtes omathear is currently in Provenance, in Threshold, Gateway to the Dream City
21:28:00: You begin evoking House Members
21:28:03: Gleali is currently in Union of the Covenant, in Threshold, Gateway to the Dream City
21:28:07: You begin evoking House Members
21:28:08: kirtes omathear is currently in Gathering of the Entranced, in Threshold, Gateway to the Dream City
We need to continue testing this further to see if it reports similarly in other rooms and planes.