Can't add env vars using web ui

(real names for ORGANISATION/PROJECT removed)

adding a new env var results in error "Error: You must choose a name for this environment variable If we can help, contact us."
https://circleci.com/gh/ORGANISATION/PROJECT/edit#env-vars

https://circleci.com/api/v1/project/ORGANIZATION/PROJECT/envvar
POST request w/ “null” payload results in:
Status Code: 400 Bad Request

Same issue here

Seeing the same issue.