The recent ATOMKI experiments provided evidence pointing towards the existence of an X17 boson in the anomalous nuclear transitions of Beryllium-8, Helium-4, and Carbon-12. The favored ranges for X17 boson couplings to up and down quarks are determined through fittings to these nuclear transitions. In this work, we consider X17 boson contributions to the previously measured $D$ meson decays, including $D_s^{*+} \rightarrow D_s^+ e^+ e^-$ and $D^{*0} \rightarrow D^0 e^+ e^-$, as well as the measured decays of $\psi(2S) \rightarrow \eta_c e^+ e^-$ and $\phi \rightarrow \eta e^+ e^-$. Using these data, we perform an independent fitting to the couplings between the X17 boson and various flavors of quarks. This fitting requires a huge X17 boson coupling to the u quark that creates a serious tension with ATOMKI's data. Our analysis models X17 as a vector boson and allows its quark couplings to be generation-dependent. The implications of our findings are discussed.