I have assembled small sample (grid-in-partial-view.zip) which illustrates how to load a grid in a partial view when change event of another grid is fired. When editing in the provided sample the partial view does not reload:
Give the attached project a try and let me know how it works for you. I would appreciate it if you modify the sample in a way that the issue is replicated and send it back. This will enable us to look into what is causing the problematic behavior.