In Details View, dragging to select multiple files only works when you start the drag from the bottom of the file list, and drag upwards. You can't start a multi file drag selection mid way through the list because it starts dragging the first file you clicked.
A margin (minimum 8 pixels for example) of blank space to the left of the file list would allow you to start the file selection from anywhere in the list by starting the drag in the left margin. Windows Explorer does this and it works perfectly.
I consider this a major flaw in the design of E++, and I hope it will be treated as high priority.