I first removed wallpaper and marked the walls pretty badly in the process. So I patched with spackle, sanded and primed with an oil base Kilz primer. I let it dry for 48 hours and painted with a semi-gloss deep purple Glidden paint.
Needless to say, every blemish and imperfection showed when the paint dried. Four weeks later, I decided to change the color and the sheen, so I started to scuff/sand the existing wall. As I was doing this, the paint started peeling like rubber on most of the wall, but not all. What do I do next to prepare to paint again while avoiding peeling? I bought a Ralph Lauren textured paint to hopefully hide most imperfections this time around.
Also, why did the paint peel like this? I’ve never seen this happen, it came off in sheets in some places.
Stop sanding the paint! I'm sure you already figured that out. Sanding isn't necessary in this situation. You did everything right and the Kilz primer sealed the walls. The problem is the Glidden paint, possibly a bad batch. It should have cured after 4 weeks.
I recommend you reprime your walls, sealing the Glidden paint. Kilz Oil Base is a very good primer for this. Allow it to dry overnight then paint with the Ralph Lauren.
The Ralph Lauren textured paint is difficult to use. Make sure you carefully read the instructions on the can. It will hide some imperfections, but don't be surprised if some still show. Plus it doesn't cover as well as paint. Plan on at least 2 coats, maybe more.