This ruling replaces all previous ones:
1/ If a model is advancing through a different model and loses the ability to do so while the bases are overlapping, it moves to the last legal position and resumes movement if possible. The same is true if it is moving through terrain and loses the ability to do so.
2/ If a model is involuntarily moving through a different model, and loses the ability to do so while the bases are overlapping, it stops moving and you apply the rule of least disturbance.
This deals with all questions regarding Spirit Chaser, Treewalker, free strikes from Incorporeal models, et al.
yup incorp modellen zijn net nog beter geworden ^^