The IRS does not have any authority to waive excess-contribution penalties. The exact amounts of excess contributions made for 2019 through 2022 will need to be distributed from your son's Roth IRA(s) before the end or 2023 to avoid another 6% penalties on these on 2023 Form 5329. These will be nontaxable distributions of contribution basis.
Your son has until the due date, including extensions, to obtain a return of contribution of an 2023 excess contribution, with the amount distributed adjusted for investment gain or loss, to avoid any penalty on the 2023 excess contribution. The 2023 excess contribution returned in this way will be treated as not having been contributed.
