The issue isn't that it took a long time to fix the problem, I work in a problem solving environment and can understand the "oh, this will fix it in ten minutes, oh no, it wasn't that" feeling. However as some other have said (strangely not rail staff), those on the outside (i.e. not the train crew, fitters etc) should have been mobilising other options as the time was ticking by. No you don't bring it the sherpas and helicopter rescue ten minutes in, but you do for example, think about getting some supplies onto a passing train 2 hours in, if the fault gets fixed before it gets there then you just don't use them.
From the outside it doesn't appear that any contingency plans were started, let alone used. Start the procedures rolling, supplies, staff, other transport, and if the fault gets fixed than cancel them
After the Thameslink passenger escape incident, the risk of similar happening should assessed with to be included in the plans for dealing with similar situations. (e.g. after on hour 1% chance, after 4 hours 5% chance, DOO train increase chance by 2%, etc) Passengers shouldn't do it, but the risk that they will needs to be allowed for,