Glossary
Slot remnant
Leftover pixels of an older tile in a legacy bcache*.bmc slot, visible when a smaller tile was later written into the same slot.
Legacy bcache*.bmc files store tiles in fixed-size slots. When a smaller tile is written into a slot that held a larger one, the unused part of the slot can still contain part of the previous tile. That leftover is a slot remnant.
Remnants can show content that is otherwise gone, such as the title bar of a window closed long before. They are fragments, may belong to a different moment than neighbouring tiles, and should be reported as such. bmc-tools exports them with -o; RDP Bitmap Cache Parser flags them. See the bcache*.bmc and Cache*.bin file format.