Nest resets cool temp

I’m hoping someone can help!

So if I set my Nest to cool at 70 which will be 5 degrees cooler than it is, then AC will engage. After it’s reached that temp the next “cool down” will set it self to like 80 degrees! I don’t understand why it would reset the set temp for engagement

Also, if I set my AC while away, you know so I can come home to a cool house, it won’t engage until I’ve opened the door and come into ‘proximity’ of the house. Sort of absolutely defeats the purpose

Does anyone have any insight? Thank you!