Curiouser and curiouser...
Is there a threshold beyond which the ancestor and descendant buttons are activated? I see both of them on the profile of my great-great-grandfather Gaßmann-265, and I see the ancestor button for Deiß-75, but not the descendants button --- even though he has (currently) one son linked in the tree. (Even if there were no descendants at all, a pop-up window would be preferred to no button at all.) Deiß-71 has one ancestor (no button) and several descendants (with a button).
Very confusing!