Help! QLDer painting issues 😊

Hi team, We have a Queenslander with new Pacific Jarrah stair treads which we oil with Cutek. We also have lovely white tips at both ends of each tread as is the fashion for a QLDer. Now while we love this look and love the look of our beautifully oiled deck, our white painted ends keep crumbling off. We have used two top brands of oil based undercoat (Taubmans Prime and Seal and Zinsser oil based primer) and the top cost is Taubmans Alklyd. It seems like the oil seeps under whatever paint/primer we use and kicks it off. Surely other Queenslander painters/ carpenters/ experts have had this problem before?