This must be a common one: my caree's assessor decided that she could walk 200 m (outside on level ground), no problem, on the basis of seeing her take maybe half-a-dozen steps on carpet in her lounge. Never mind that this totally contradicted everything she'd said about on a good day possibly being able to walk the 3 m down to the garden gate!
Plus there were the usual comments about looking kempt (as if that affected her ability to walk) and making eye contact throughout, when she sat there most of the time with her eyes shut.
So yes, I find it really frustrating to be told not to bother trying to challenge such things when they're so obviously inaccurate and remain on her report to influence the assessment.