Hi,
passing on the observation. I’m using Multichannel mode on a real design (tentatively but looking good), documenting the glitches I run into.
When the “Group items with their target group areas” switch in “PCB: Tools/Multichannel/Repeat layout” is enabled, I get occasional inclusions of a “ghost group” around the top left corner of the drawing sheet (this might be some sort of origin). It shows as a zero-size group (magenta with default settings) which isn’t selectable. I fixed this once by removing all groups with a text editor from the pcb file.
Symptoms are that clicking on any component in one of the target rule areas after “PCB/Tools/Multichannel/repeat layout” randomly does not show a selection the size of the target rule area but a much bigger group that appears to include the top left drawing sheet corner.