If you have an object that is not the size you want it to be then edit its group/instance, and use the tapemeasure tool to pick two points across it [typically two vertices] - let's say the VCB reads '~456,7mm', but you want it to be say '18mm'... then simply type 18mm <enter> [as you would for many of the native-tools that will take VCB inputs] and when the dialog asks if you want to scale everything you must answer 'Yes'. If you now pick the same two points the VCB should now read '18mm'.

The 2d import is located very far above z=0, which doesn't help... BUT the 2d plans were obviously imported from a CAD file [dwg/dxf?] and they contain some rogue geometry that's miles off.
If you edit that component [double-click it], then use edit > 'select all' [ctrl+A], and then deselect the visible parts by using select+fence whilst holding shift+ctrl, then press 'delete', the 'unseen' CAD file's rogue geometry that's a zillion miles away [and totally useless to you anyway] is removed... then the whole thing works OK with the wall faces displaying properly etc etc.
The extents of the model were so distorted by this issue that SUp couldn't properly calculate the visible geometry, so faces went weird... 😕