Well, in the effort to bound the (almost) duplicated node issue, I've made many tests. I've built the simplest map that reproduce the error: 6 nodes and 5 arcs. You can build one by yourself, compile with mkgmap, and it always crashes mapsource routing. The interesting things is that the routing is broken if, and only if, the two collapsing nodes are connected by an arc and are also connected to (at least) 2 others arcs each one. So if you just have a highway with two so close nodes that will collapse during encoding, no routing issue will arise. I attached a png that shows the topology that triggers the problem. For your info, if the nodes distance is 3.4 meters or more, there is no possibility of collapsing in a level 24 map. If they are 1 meter apart, there is 50% possibility of collapsing. More or less. Ciao.
