Have you tried introducing a food scale? Not with the intent of changing your portions or anything like that - just out of idle curiosity to confirm how much you're eating?

I found that I was eating over double the amount of nut butter that I was estimating once I started weighing it. After a couple of months I was able to go back to eyeballing it while remaining accurate.

A lot of wisdom suggests being +/- 300 calories from your TDEE to cut/bulk. Three tablespoons of peanut butter is ~285 calories. So it's entirely possible that something as small as an estimation error is responsible for whether you're gaining or maintaining. Same goes for eyeballing cooking oils, seeds & nuts, and, to a lesser extent, processed carbs.