We asked the bank for a statement on the MAS5 "mortgage prisoners". Here is their response (28 March 2023)

“We remain committed to providing our customers with the support they need and achieving good outcomes for them based on their individual situations.
We have proactively sought ways to assist customers that could be considered as mortgage prisoners, implementing the ability to re-mortgage, subject to eligibility, and in line with our commitments as a responsible lender. We've previously co-operated with the All-Party Parliamentary Group on Mortgage Prisoners on any questions asked and will continue to do so.”