Issue with gmx do_dssp: Missing Secondary Structure Data for One Residue

GROMACS version: version 2020.4
Hello GROMACS Community,
I am encountering an issue while using gmx do_dssp to analyze the secondary structure of my protein. My protein contains 42 amino acids, but the output from gmx do_dssp only provides secondary structure data for 41 residues.
I have verified that my input files (trajectory and structure) correctly represent all 42 residues, and I am using the DSSP executable located at /usr/bin/dssp.
Could anyone suggest possible reasons for this discrepancy and how to resolve it?
Thank you for your time and assistance!

Best regards,
ishwar

can anyone please help me regarding this.