The tangent is a unit vector along the path - it has nothing to do with the force. However, the force on each atom is less than 0.01 eV/Ang:
FORCES: max atom, RMS 0.007795 0.003173
and so this image is converged. To check the entire band, you can use the nebef.pl script, which will grep for the force on each image and then you can see if they are all below 0.01 eV/Ang; at this point the calculation will converge.
Problem in interpolation with nebmake.pl script
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