Error with find(X) statement

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I'm trying to run a simple calculation to find the non-trivial columns of a unitary matrix. All the unitaries in this case are of the form:

[ 1 0 0 0,
a b 0,
c d 0,
0 0 1]

where a b c d form the 'non-trivial columns', in whatever columns.

Which is to say, if you sum the matrix either column wise or row wise, the sum must always equal 1, or be the non-trivial columns I'm trying to find. So the way I'm doing it is:

states=find(sum(UNITARY_MATRIX)~=1.0)

Which generally outputs something like:

Unitary number: 5
   1.0000 + 0.0000i   0.0000 + 0.0000i   0.0000 + 0.0000i   0.0000 + 0.0000i
   0.0000 + 0.0000i   0.8165 + 0.0000i   0.0000 + 0.0000i  -0.0000 - 0.5774i
   0.0000 + 0.0000i   0.0000 + 0.0000i   1.0000 + 0.0000i   0.0000 + 0.0000i
   0.0000 + 0.0000i  -0.0000 + 0.5774i   0.0000 + 0.0000i  -0.8165 + 0.0000i
sum of column values
   1.0000 + 0.0000i   0.8165 + 0.5774i   1.0000 + 0.0000i  -0.8165 - 0.5774i
Non trivial columns:
     2     4

This is working very well for all the unitaries I'm checking, except for the following: (this is the output in the terminal)

Unitary number: 6
   1.0000 + 0.0000i   0.0000 + 0.0000i  -0.0000 - 0.0000i  -0.0000 - 0.0000i
   0.0000 + 0.0000i   1.0000 - 0.0000i   0.0000 + 0.0000i  -0.0000 - 0.0000i
  -0.0000 + 0.0000i   0.0000 - 0.0000i   0.7071 - 0.0000i  -0.7071 - 0.0000i
  -0.0000 - 0.0000i  -0.0000 - 0.0000i   0.0000 - 0.7071i   0.0000 - 0.7071i
sum of column values
   1.0000 + 0.0000i   1.0000 + 0.0000i   0.7071 - 0.7071i  -0.7071 - 0.7071i
Non trivial columns:
     2     3     4
  

Any idea why this is happening? This is the only matrix this is happening with. Since clearly the non-trivial columns should be 3 and 4. Is this to do with how find(X) reads complex numbers?