DWP Thwarted Appeal

My adult daughter who is very poorly went onto ESA last year. In May, following an assessment which gave 0 points, she was taken off ESA, so we asked for a Mandatory Reconsideration which was not changed so we asked for an Appeal. In the meantime due to new serious medical conditions she was put back on ESA. Before the appeal was heard, the DWP decided to put her in the Work Related Activity Group instead of the Support Group, but because they said their decision was 'favourable' it has stopped the appeal going ahead & we have had to start a new Appeal. It seems by continuing to make erroneous decisions the DWP can actually stop the claimant from appealing. How can this be right ?