Electron affinity of isotopes anomaly

According to the [Wikipedia article](https://en.wikipedia.org/wiki/Electron_affinity_(data_page)) the electron affinity of $\ce{^{2}H}$ is higher than the electron affinity of $\ce{^{1}H}$ however the electron affinity of $\ce{^{18}O}$ is lower than $\ce{^{16}O}$. How is this anomaly explained?


