DWP data sharing - what should I ask them to disclose?

I had an ESA overpayment hearing today that was adjourned to give the DWP a chance to respond to some points raised by the appeal. I’m helping the client (on ESA/PIP) challenge an £11k overpayment of severe disability premium caused by her cousin starting to claim Carer’s Allowance in 2018.

The judge has asked me to submit a request for disclosure as well as questions to put to the DWP about their data sharing systems. The appeal response says that these systems are “not mandatory” and “used irregularly”.

I am going to ask if there was a policy governing data sharing between different benefit teams within the DWP in 2018, what systems existed then, how often the system/systems was/were used, what prompted the system/systems to be used, and whether there have been any changes to way the system/s are used in the last 5 years.

I would be really interested to know what other questions people think I should ask, and if there are any specific policies or documents that people would like me to ask to be disclosed.

Sharing notifications of changes e.g. addresses, composition of household.