For further explanation (can’t remember if I’ve explained this before). The FTV (“descendants” or “Overview”) does work OK in 99.9% of cases.
Even in the 0.1%, as shown in your example using the GEDCOM file “Historic” you sent me, does still work. The issue is that it is very slow, requiring > 150 seconds (‘max_execution_time’) to produce a result (at least on my servers). That was not an issue in previous versions of kiwitrees, and is not an issue in justCarmen’s webtrees version.
This is due to complexity of some relationships, not the size of the tree.
I believe it is due to the new relationship algorithm we are using in kiwitrees. That is the only significant difference between the kiwitrees version of FTV and justCarmen’s original. It was written to make the relationship chart perform better, but (so far) seems to have made FTV slower.