The board's layer objects and the Layer Stack Manager each hold a copy of the stack. "A script write to the board's stack (pcb_set_dielectric, pcb_modify_layer, a rebuild) does not reach it, and the manager goes on showing, and on its next apply writing back, the old values." There was no way to see that from a script. The new read-only tool compares both and reports out_of_step. Verified live on a real 8-layer board: after setting Dk 4.35, the manager still said 4. This is the cleanest example I've seen of two copies inside one vendor tool.