Welcome to CADTutor.
Enter QLEADER at the commandline, then enter S for settings,
and you will see the LEADER definition dialogue box.
My guess is that your maximum number of points for the leader has been
set to 2, perhaps while using a lisp program which was cancelled midprocess, thus leaving your setting changed. and unrestored to your previous setting.
Set it to 3 or more, and you may want your tail set to land horizontally?
The multileader settings also include similar options, but as you pointed out QLEADERS are not MULTILEADERS.