One example (save in test.csv and load undirected):
0,1,2,3
1,0,4,5
2,0,6,7
3,0,8,9
4,1,6,8
5,1,7,9
6,2,4,9
7,2,8,5
8,4,3,7
9,3,5,6

The network diameter is (correctly) calculated as 2. But the heatmap and shortest path features paint/calculate longer distances than 2 on some nodes/pairs. Just use heatmap on multiple nodes and some of them will show a max distance of 3.