My house had a quick paint job on the walls and trim to get it 'presentable' for the market. Now that I bought it and lived here a while, there are places where the paint chipped off. When I repainted one room some of the trim paint came off when I peeled the masking tape off.

I doubt there was much prep work done before the walls and trim were painted.

Should I scrape the whole walls and trim before I repaint? Should I start with new trim instead? Anything I can do to make the paint adhere and not chip off because of old layers?