Hi @maiki, thanks for looking into this!
Here’s a CURL request you can use, which was generated from postman (if you’d like). This generates a 500:
curl --location --request POST 'https://XXX.com/users.json' \
--header 'Api-Key: XXX' \
--header 'Api-Username: XXX' \
--header 'Content-Type: application/json' \
--data-raw '{
"name": "XXX",
"email": "XXX@mail.com",
"password": "aTestPAssword",
"username": 1,
"active": true,
"approved": true
}'