What I am doing
1. Files sorted by date taken to ensure originals and duplicates are together
2. select dup image to be removed.
3. If more than one dup of image, press control shift on last of series.
4. Holding down right mouse button, drag all duplicates of image to new location (a folder I created specially, as I wish to erase rather than delete i.d.c.
5. On appearance dialog box select "move here".
As that has worked hitherto I'm puzzled.