Homemade potato chips

I tried baking potato chips for the first time and they turned out awful, just burnt or soggy.

I used skinned red potatoes and cut them with a Mandolin as small as it could go, patted dry, then brushed with olive oil and baked at 400 for 20min. At that point a couple were burned but most looked still uncooked; so I dropped it to 375 and gave it like 8min and none of them looked nicely cooked in that time. Either all burnt or still soggy parts.

Any ideas what I could fix?