Perhaps I am missing something but the merger tree links found e.g. for subhalo with ID 11505, snapshot 21, TNG50-1, in https://www.tng-project.org/api/TNG50-1/snapshots/21/subhalos/11505/, seem broken.
Would you suggest disregarding this subhalo as a consequence, or is there some other way to access the merger trees?
Many thanks in advance!
Not every subhalo is in a given merger tree, and it looks like this one is one such case.
(Any merger tree related analysis would not make sense for such a subhalo).