To reproduce

1. Open attached scene and load 'baumumbau' scene
2. select 'Tree A' and extend the length of the uppermost trunk (or branch, not the leaves) and extend it via the slider

Following error message:

Quaternion To Matrix conversion failed because input Quaternion is invalid {-1.#IND00, -1.#IND00, -1.#IND00, -1.#IND00} l=-1.#IND00
UnityEngine.Matrix4x4:TRS(Vector3, Quaternion, Vector3)