Furniture, Wood and Cabinetry Finishing - Stain not "sticking"...

I'm in the process of restaining my kitchen cabinets. Currently, I'm working on the face frames. I sanded down the existing red oak cabinets in natural finish and stained 2x with a General Finish Espresso stain. I'm happy with the result and have an idea how much stain the wood "soaks" up.

The problem: I bought two more cabinets that matches the existing design. I bought them in red oak - natural finish. I wen through the same procedure (sanding and staining). The issue is that the front of the face frame hardly absorbs any stain. I have not the same issue on the sides of the frame. What could be the problem?

You may not have removed all of the previous finish. Also some woods are harder than others which means less stain penetration - even in the same species.