Unable to add user to project role

I am trying to add a user to a project through the REST API and getting a very strange result. Using Postman to test, here is what I see (headers are removed):

curl --location 'https://xxxxx.atlassian.net/rest/api/3/project/PDSSUP/role/10200' \ 
--data '{
  "user": [
    "62137372802e7600754781d"
  ],
  "groupId": []
}'

This should add the indicated user to the indicated role. However, I get the following error message:

"We can't find 'ug:347c7eb0-d1d7-47f2-8692-8e734b0087d2' in any accessible user directory. Check they're still active and available, and try again."

I don’t understand why it is looking for a user with a different id than what I passed in.

If I look up the user with the original id, they are valid in the system:

curl --location ‘``https://xxxx.atlassian.net/rest/api/3/user?accountId=62137372802e7600754781d’``

returns a valid user

Am I doing something wrong? Is there a behavior that I am missing?

Hello @derek.fields

The Add actors to project role endpoint allows you add users OR groups to a role, maybe not both at the same time? If you remove the empty "groupId": [] array declaration from the request body, do you get a different result?

Also, is the fault happening with the user ID of every single user, some users or only that one user?