Hi Claira, I've been going through the same thing for months also. Today I had my MRN denying back pay for engaging with people face to face under the Leap Review. The DM based her refusal on my original assessment report from June 2017 which was in fact a pack of lies resulting in 0 points for both Mobility and Daily Living. After submitting two pages of A4 written testimony exposing the lies and misleading information I was awarded both components at Standard rate (2 points for engaging with others btw). I know I was underscored but to uphold a dodgy decision from 5 years ago? I am also upset and distressed.
Keep writing, regardless. Take the MR route if you haven't already done so!