I mean... It's probably just the sheer amount of track and trains - it just about works in reality without things going wrong, imagine how bad it'll be with the TSW dispatcher, let alone the frame rate? You've got 2 major junctions to the north where Thameslink and services from Cannon Street join, then you've got this massive artery of track stretching a good half a mile (possibly more), then another series of junctions as the BML leaves, and the suburban lines branch off. It is (or at least was until recently) one of the most congested bits of track in the entire country. It's not exactly going to be a walk in the park and may well be much worse than Victoria, albeit perhaps not as bad as Waterloo or the SW side of Clapham.