In the attached file are 2 curves on different layers.
When I select them both at the same time and try to change them to Upper Walls in the Object Properties dialog, the one on Lower Walls doesn’t change layers. Selecting them both and changing to Default or Lower Walls at the same time works correctly.
(8.0.22319.12305, 2022-11-15)
Until this is fixed, select your objects and then right-click on a layer, in the Layers panel, and pick “Change Object Layer”. You can also poke the “Change Object Layer” button on the Layers panel toolbar.