Identical appeals, different outcomes

Seem to have a bit of an unusual situation, as seen nothing on threads similar. My wife and son parked their cars in a car park at the same time, and were both issued PCN's as we were not 'patrons' of the establishment (big leisure complex car park). Both appealed to the operator (signage was poor);unsurprisingly, both rejected. Both were then appealed to the IAS, using identical wording in both the appeals. My wife's appeal was upheld by the IAS (great, we thought, son's will be as well). Twelve hours later, my son's appeal was dismissed! When questioning this to the IAS (not easy, as they really don't want anyone to contact them; we ended up getting the operator to contact them on our behalf), the excuse we got for this was the two appeals were looked at by different (anonymous) adjudicators, and once a decision had been made, the IAS are unable to interfere with the adjudicator's decision, as 'this would compromise the independence of the service'(!). We then asked for comments on how this could happen from the Lead Adjudicator Bryn Holloway, named on the IAS website. Surely a precedent had been set with the first decision? Several months later, still no response.
We're now getting letters, first from ZZPS, and now their tame solicitors Wright Hassall, 'encouraging' us to pay the fine, and how to easily do this. Just curious if anyone has any advice on this; two identical appeals (following their prescribed appeals system) with different outcomes? Can they enforce the one supposedly issued correctly, when we have evidence stating an identical one was incorrect?