Angular 1.6.4 $watchGroup returns empty strings for old values. I don't understand what's wrong?

Question

JavaScript

Actually, all the old values ​​are returned empty and I can’t find out what happened before (pasting into the input form fields is performed from the clipboard): However, after a while after several changes in the fields in manual mode (by pressing keys on the keyboard), everything returns to normal and the old values ​​are already specified normally. If I enter everything manually at once, without using the clipboard, then everything seems to be normal. $watchCollection gives correct results. Here all the old values ​​are specified correctly. ??? There are absolutely no ideas what is wrong.

Answer 1

I recommend that you abandon $watchGroup and $watch, instead add ng-change to the inputs, and do whatever you want in the handler functions.
Reasons:
1) Full control of the process
2) No performance loss due to watch'ers

Answer 2

What for in principle watchCollection? Do you have ng-model there? Use ng-change. Well, all sorts of convenient buns for working with forms, since angular is fine with this.
Well, the problem is not in the watchCollection, I threw in the minimum option here - everything works:
plnkr.co/edit/YOaCVdKyav5Q9OuXxY8B?p=preview