A large area outside of my fort at Z-level 135 is designated to have floors constructed on it. Shortly after the job designation, a sapling at Z-level 134 grew into a tree that extends up to Z-level 137. When dwarves atttempt to construct floors occupying the same tile as the tree, Dwarf Fortress crashes.

The Z-135 portions of the tree trunk/branches are only revealed after canceling the "Construct Floor" designation on the tiles where it has appeared.

The tree trunk location is approximately 85 tiles north and 70 tiles east of the map's SouthWest corner, at Z-level 134.