Gratuity related

Respected Sir/Madam, My father - in - law retired from BEST - Mumbai bus service 5 month ago, He was Co- surety to his friend's car loan taken form cooprative bank in 2014, His friend has defaulted loan installment, Bank approched to the assistant Registrar, Cooperative for order to recover money from principal debtor and sureties, accordingly the assistant Registrar given the order in 2016, After 2016 , the principal debtor is absconding and sold his Agricultural land which was given as a security to the Cooperative Bank 2019 ,and another co surety not able to pay the amount of loan and interest to Bank , bank started recovering loan money from my father- in -law's salary from 2017 till 2022. Bank didn't mention the loan amount on that government satbara 7/12 and principal debtor sold his land, also Bank has taken car from that principal debtor in 2016 and sold it to another person without taking it on record and not doing auction of that car, Now for remaining amount of loan and intrest , Bank has given letter to gratuity officer of my father- in -laws office and ask not to release gratuity amount till bank gets all remaining money. This is a complete injustice with my father in law , how can my father in law take his gratuity amount and punishes to the bank officers for their omission and commission of illegal acts and recover the given installment of loan from the principal debtor and another co surety.