AMS screen must be set such that each slot shows a different material type or color. Bambu printers will try to substitute slots with similar material and a toolchange between slots with the same material and color set may be ignored.
The actual physical material and colors loaded do not need to be different or accurately reflected in the printer screen or slicer Device tab. Only the material/color shown on the printer or Device tab need to be distinct from each other.
Auto Refill should be turned off.