The Free On-line Dictionary of Computing (19 January 2023):

mandelbug

    /man'del-buhg/ (From the Mandelbrot
   set) A bug whose underlying causes are so complex and
   obscure as to make its behaviour appear chaotic or even
   nondeterministic.  This term implies that the speaker thinks
   it is a Bohr bug, rather than a heisenbug.

   See also schroedinbug.

   [Jargon File]

   (1995-02-08)


The Jargon File (version 4.4.7, 29 Dec 2003):

mandelbug
 /man'del·buhg/, n.

    [from the Mandelbrot set] A bug whose underlying causes are so complex and
    obscure as to make its behavior appear chaotic or even non-deterministic.
    This term implies that the speaker thinks it is a Bohr bug, rather than a
    heisenbug. See also schroedinbug.