Failed to set breakpoint

I have a file loaded containing the following generated predicate among others.  Pcemacs refuses to set a breakpoint on any line contained in it.  Other predicates in the same file, no problem.  But all predicates looking like this, problem.  If it matters, loop29 is generated, and the next time the file gets generated it may be called loop34.  

loop29((Object, Key), [RefVar|M39], [ActiveVarId|N39]) :-
( ( RefVar= (Ref=_),
    wait_instance_active(Object, Ref, ActiveVarId)
  ),
  true
), !,
loop29((Object, Key), M39, N39).

loop29(_, [], []).

 
Alan Baljeu
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