ERR_NGROK_SHIP_ENVIRONMENT_VAR_VALUE_EXPRESSION_INVALID: Environment variable KEY has an invalid expression: REASON - ngrok documentation

What does ERR_NGROK_SHIP_ENVIRONMENT_VAR_VALUE_EXPRESSION_INVALID mean?

ngrok returns ERR_NGROK_SHIP_ENVIRONMENT_VAR_VALUE_EXPRESSION_INVALID with this message:

Environment variable <KEY> has an invalid expression: <REASON>

Where can I get more help with ERR_NGROK_SHIP_ENVIRONMENT_VAR_VALUE_EXPRESSION_INVALID?

Email support@ngrok.com and include the error code.