Running Win 11, Fences 4 on a new machine - nothing carried over so it is reasonably clean.

If I have a Fence with a number of files, and I use the mouse to cover all of the files so as to select them all,  Fences always misses the upper left file and often the file below it. 

Pink is the Fence.  Purple is the physical area selected using the mouse.

Light purple is actual files the mouse selected.

Note that the mouse is in the upper left but the selected area did not follow it and therefore did not select two files.