Gee, l'm glad l'm not the only one! 😅
l have a Janome 8900 , love it, but it has an acrylic extension table with a slot for a moveable seam guide. So many times, l've sewn only a single layer of fabric, finding the bottom piece below the table as the slot diverted it away from the foot! I've since put tape over it, but must remove it when using machine's sleeve arm. Sigh.