Complex TreeGrid and Comboboxes not showing.

I'm beginning to feel like comboboxes have a personal vendetta against me, my family and everyone I know and love.

I'm trying to do a complex tree grid with objectives (that are comboboxes), and sub objectives (that are a textbox, and two other comboboxes). I've gotten to the point to where the tree panel renders, and blocks out the "Assigned To" and "Status" columns on main objectives. Only thing is, I can't seem to get the comboboxes to show their data, and it populates with "[object object]". So after working on this all day, I'm at my wits end and need another pair of eyes on this.

https://fiddle.sencha.com/#fiddle/e79

And I'm using a viewmodel on this treepanel, since it seems like the legit thing to do (this will go into an MVVM scheme in my project).

Many Thanks.

Complex TreeGrid and Comboboxes not showing.