IIDB - supersession due to ‘new medical evidence’

Hi
Does anyone have a view on this - I’ve got something pinging in the back of my head but can’t quite put my finger on it.

Background - Client has a pre-existing knee condition, reconstructive surgery done March 2016, appears to be recovering nicely. 
Has 2 accidents at work in September and October 2016.  From then on, her knee is in a state, goes into spasms, has frequent falls, no treatment is particularly effective.

Client claims IIDB in Feb 2019 - assessed as being 35% disabled for life. 

Client also makes a Personal Injury claim against her Employer.  In the course of this claim 2 medical reports are produced - one supporting the notion that her problems are as a result of the accidents at work, the second does not support this and takes the view that it is her pre-existing condition which has caused the problem and the injuries from the two work accidents would have resolved in time.  The second report was produced by a Specialist acting for the Employer.  Very shortly after this report was produced the Employer made an unexpected and large offer of settlement, which was accepted.
The Employer’s solicitor’s appealed against having to pay the IIDB paid during the claim and as part of the process sent the 2 medical reports to DWP.

DWP decided to supersede the IIDB award based on the second report (they appear to have ignored the first report which agreed with their initial decision which was that the knee problems were caused by the accidents at work.

Whilst I’m not particularly surprised at this, it does seem that the situation is ‘oh we like this version better’. 
Is it ‘new evidence’ or is it a different opinion?
What, if anything can I do about it?  I have the vaguest recollection of a case like this but cannot remember any details, anybody help me out?
All suggestions gratefully received.

If this is a “final” award for life, the starting point must be identifying a change in the claimants’ circumstances or a mistake as to ignorance of some material fact that could provide the ground for supersession (Reg 6(2)(a) Social Security and Child Support (Decisions and Appeals Regulations)
There is no provision regarding industrial injures benefit equivalent to Reg 6(2) ((g) or (r) (receipt of medical evidence relating to incapacity for work or limited capability for work- or work-related activity) so the mere fact of receipt of a new medical report, regardless of the source of the report is of itself not grounds for supersession.
The report may however reveal some relevant material fact that the decision maker was ignorant of or was mistaken about.
A material fact is one that the decision maker ought to have considered and which could have influenced the result (See Saker V SOS reported as R(I)2/88)
A material fact is a primary fact as opposed to a secondary fact which is a conclusion deduced or inferred from a primary fact thus a difference of opinion as to conclusions to be drawn from a primary fact cannot be grounds for revision or supersession (see R(S)4/86, RH v Secretary of State for Work and Pensions (DLA) [2015] UKUT 0453 (AAC))
If the DWP want to rely on the new report as the basis for supersession, they will have to point to some specific fact revealed by the report that was previously unknown or some clear and obvious mistake that had been made when that fact was considered. 
They cannot rely on the report as a whole or the opinions of the professional who compiled the report

Thank you Stainsby - that’s it exactly, you’re a legend