UC and IT failure on DWP part

I have a lady who claimed UC in which payment amount was disputed so a MR was submitted via journal, paper and in person she then added partner at a later date this has caused the DWP to lose her claim prior to the change of circumstance.  Has anyone experienced this?

If so what tactics did you use?

I am re submitting the MR for the 5th time and am submitting a complaint and a request for financial compensation. 

it is beyond ludicrous that they cant find the initial claim they are stating that no MR was submitted.  It concerns me what they have done with her data.

appreciate any tips.

thanks