It’s probably because Eevee is missing its evolutionTargetId if I have to guess.
{
"speciesId": "ae920eed-c027-46b0-822a-32e89444a9d8",
"species": {
"name": "Eevee",
"canEvolve": true,
"evolutionTargetId": null,
"evolutionMethod": "happiness",
"evolutionCost": 80,
"shinyProbability": null
}
}