Therefore I contend that the Forum site is wrong to be offering 1st Class with the higher prices for passengers to then find that the train does not have 1st Class.
If you're going to suggest it's broken, could you maybe spend at least spend 2 minutes checking whether it is or not first before making a thread about it?
Firstly, customers are very clearly told where first class accommodation is unavailable:
This is also shown again on the Ticket Information screen:
Secondly, if first class isn't available on one half of the journey, the fares engine will do its best to swap in standard class fares where this would be cheaper for the passenger according to the planned itinerary:
In this instance, I am only being charged for first class on the train which has first class accommodation.