We identified SELFIES strings that generated atomic valence errors. Although the SELFIES-to-SMILES conversion module imposes corrections like atomic valence constraints to ensure SMILES validity, its default settings nonetheless raised RDKit explicit valence errors in some cases (Figure ). Although errors, most of these edge cases were easily correctable. We introduced a "Modified Constraints" correction (described below) that modifies invalid SELFIES by altering formal charges for atom tokens that raised errors in RDKit By manually inspecting the VAE-generated invalid SELFIES strings, we identified six Troublesome SELFIES atom token 1.