When you update an MVVM model using the proper "set" method, any validators tied to controls tied to the model do not fire. I'm assuming it is because the validator is wired to the "blur" event of the textbox. I would prefer to not wire the validator to the "change" event, if possible.
For example, I have a textbox that is required. If I blank out the value, the validator fires correctly. If there is some other action that changes the model, the validator does not re-execute and therefore remains.
I've made a simple Dojo that represents this.Blank out the textbox, tab or click out, and then click the "Alter Model" button.