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Precision, symmetry and POSCAR

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VASP determines the symmetry of the system from the POSCAR file. It is a common mistake, to enter the positions with insufficient precision (too few digits). To make the best use of the symmetry routines in VASP, it is strongly recommended to specify the positions (and lattice parameters) in the POSCAR file with at least 7 significant digits. Internal tests for symmetry operations are done against a user supplied value, specified by SYMPREC (defaults to 10-5). Hence, 5 significant digits are absolutely borderline and can cause serious issues in the automatic symmetry determination, for instance, finding some but not all generators for the symmetry group. Also "noise" in the positions might grow during relaxations, so that sometimes, upon reading the CONTCAR file, some symmetry operations are missed. All these issues are best avoided by making the initial POSCAR file as accurate as possible.