Hello,
the error message indicates that a quartet spin state breaks the C3 symmetry.
IRREPS of e-type in C3 symmetry are paired. So the e-MOs 1 and 2 must have identical energy and occupation, 3 and 4, etc.
If one of the pairs is empty, the error message is just what you got. For partly filled orbitals there will be a warning:
WARNING
Symm. of e-repr. not preserved in ... cases
Max deviation in the symm. blocks: ....
WARNING
Antisymm. of e-repr. not preserved in ... cases
Max deviation in the antis. blocks: ....
Regards,
Uwe