This problem could be caused by the surface tension of the oak. Surface Tension, sometimes created by sanding, can cause stains to not adhere to the grain of the wood.
You have a few options:
A high-performance 2K coating has a base specifically formulated to be catalyzed with Isocyanates to crosslink the polymer fully. This catalyst provides superior performance over 1 K coatings that have been hardened with PolyAzuradine or Carbodiiamide. To create Enduro Tintable 2K; General Finishes tested over 30 polymers, resins, and other ingredients sourced from around the world.
General Finishes industrial/professional Enduro Water-based Tintable 2K coatings are ideally qualified for OEM (Original Equipment Manufacturing) production, which requires functional properties that are essential to the performance and durability of industrial, transportation, and durable consumer products. In addition to our line of stock Enduro finishes, General Finishes can custom-make coatings for your specific OEM objectives.
Toning is the process of adding colorant, either dye or pigmented stain into a top coat and then applying over an entire piece in order to subtly deepen the color. All of our stains can be used: Stock base colors of RTM, Water-Based Wood Stains or Dye stains. If you are new to toning, we recommend starting with Dyes stains, which can be easier to use as they only contain dyes and no pigments.