Delays in calculating overpayment of benefit

Is there an argument worth having if JC+ are delaying the calculation of an overpayment which the client is happy to pay back in a lump sum when the amount of benefit being received should increase as a direct result of paying the money back.

For example, say if a client had £10k savings their benefit is being reduced by £16 per week.  If the overpayment is £3k, they are potential losing out on £12 per week.

I think you’re either looking at letter before action and threat of JR, or look at Financial Redress for Maladministration once situation resolved.