Found the problem and how to get around it.
If you have a Phone attribute and in the attribute dialog at bottom and you set to Validate as "US Phone" and then you also have a "Mask Edit" set for your Mobile forms, you will get Validate Error and can't save the data.
To solve that, if you want mask edit, first remove the Validate rule on the attribute. Secondly, it seems like Mask does not work on actual Android form. So you need to remove the Mask Edit for your Mobile form, but you still can have the Mask Edit on your Desktop form.
This will solve/get around the problem.