Administering nil rate band trust with debt/charge scheme

I have been passed the estate of a widower (died 2024) whose late spouse set up a nil rate band trust in her will with the debt/charge scheme. The property against which the charge was placed by the trustees was sold last year and remains in a bank account.
The sale proceeds were not declared on the IHT400 and the residence band was not claimed but probate was granted (the charge was deducted from the estate). Even with the sale proceeds included there is still no IHT provided we can claim his residence nil rate band now.
Is a Corrective Account necessary at this stage and will we have to reapply for probate given that the values are different?