A possible bug in symbolic limit function regarding complex entities?

The code I tried

>> syms z;

   F=1/(z-1)^2+3/(z-1)+5/(z+1i)+6/(z-1i)^2+1/(z-2)^2+1/(z-2) % original function,

   f1=(z+1i)*F % I want to cancel (z+1i)  term in denominator, by multiplying F,

   f1=simplify(f1) % the term (z+1i) still there in denominator, although can be

                   % cancelled manually,

   L=limit(f1,z,sym(-1i))

An error occured

mupadmex

Error in MuPAD command: Assumptions are inconsistent. [property::_assume]

Error sym/limit (line 47)

    rSym = mupadmex('symobj::map', args{1}.s, 'symobj::limit', args{2}.s, args{3}.s);

Problem: If (z+1i) term is cancelled manually, only warning will be given, only warning message given, no error, and the answer is correct. Is there a bug in the limit function, when dealing with complex numbers? Or problem with simplify function where (z+1i) cannot be exactly cancelled?

I am using MATLAB R2014a, on MS Windows 8.1