Is it obligatory to refuse a job at the Intellectual Property Authority due to a small portion (5%) of its work being related to intellectual property rights for songs, even though the rest of its work is free from doubt?

Intellectual property rights are recognized by Islamic law and may be protected, unless they relate to forbidden things such as unlawful music or books of magic; these may not be protected. The resolution of the Islamic Fiqh Academy states that names, trademarks, copyrights, and inventions are private rights of their owners and have a financial value recognized by Islamic law. It is not permissible to infringe upon them or to dispose of them for financial compensation if such transactions are free from deception and fraud. If your work in this job does not directly involve protecting the rights of forbidden songs, and it is possible to delegate that to someone else, then there is no harm in accepting the job.