na.numerical analysis – Does Taylor-hood P2-P1 element holds for 8 points quadratic triangle P2 element and 4 points P1 triangle elements?

I’m building a CFD solver that solves N-S equation, and I use 8 points quadratic triangle P2 element for velocity and I use 4 points P1 triangle elements for pressure , after writing basic module, I have tested the python file about the local stiffness local load on element or face, they all give the right answers, but after I use a problem to solve it, it completely fails, the error is about 8n, where n is the number of step, after checking my program several time, I start to doubt that maybe Taylor-hood element is not applicable for my elements, I store all the information about u and p on the node, is this unstable?, the error is regular and I don’t think the algorithm is wrong