Incorrect notification of earnings by employer via RTI

We have a client who has an ongoing dispute with her former employer regarding earnings. The employer had reported earnings that our client had not received, which adversely affected her UC payments. She was paid cash in hand and had no payslips so is having difficulty proving this. She has raised a complaint about the employer with HMRC via our Bureau, but with no sucess so far. In the meantime, she has appealled the UC decision on the basis that her award has taken the wrong earnings into account. Her appeal hearing is next week. We understand that there is some discretion to enable UC to amend the earnings they take into account, but we are having difficulty finding any Regs specific to this problem. We have looked at Reg 61 but this relates more to late rather than incorrect notification of earnings. Anyone have any ideas?

Would regulation 61(3)(b)(ii) cover it -

‘the Secretary of State considers that the information received from HMRC is incorrect, or fails to reflect the definition of employed earnings in regulation 55, in some material respect.’

and then reg 61(4) allows the SoS to put in his own decision

CUC/166/2017 out this week - https://www.rightsnet.org.uk/welfare-rights/caselaw/item/secretary-of-state-concedes-that-where-an-employer-fails-to-notify-earnings - discusses reg 61 quite a bit - including SoS concessions