My son's ex-wife signed a form 8332. I file his taxes and have a copy. She did not follow the form as signed. Can my son file by paper with the 8332 form?

My son's ex-wife signed in court a form 8332.  She signed for future years.  2019 is my son's year as per their agreement and signed 8332.  They have joint custody and he pays child support.  His ex-wife already filed taxes for 2019, claimed their daugher, and did not follow the form 8332 as per her agreement and the form she signed.  Can we (I file his taxes for him) send a paper copy of the signed form 8332 and his taxes to the IRS for this year?  Again, it was signed by her in court and she is not following it as agreed.  She also does not follow the court agreement for joint custody as he has not been permitted to visit his daughter as per the divorce decree (he does not have funds, as he earns barely over minimum wage, to afford an attorney to assist him in enforcing his joint custody and free legal in our state will also not assist).  My son does not want the IRS to audit him and request money due to the filing the tax return claiming his daughter (per the agreement) so he is very reluctant to send the paper form in to enforce the form 8332.  Please advise.