ERR_NGROK_SHIP_ENDPOINT_TEMPLATE_NAME_ILLEGAL_CHARACTER: Endpoint template name NAME contains the illegal character CHAR - ngrok documentation

What does ERR_NGROK_SHIP_ENDPOINT_TEMPLATE_NAME_ILLEGAL_CHARACTER mean?

ngrok returns ERR_NGROK_SHIP_ENDPOINT_TEMPLATE_NAME_ILLEGAL_CHARACTER with this message:

Endpoint template name <NAME> contains the illegal character <CHAR>. Allowed: lowercase letters, digits, and '_'.

Where can I get more help with ERR_NGROK_SHIP_ENDPOINT_TEMPLATE_NAME_ILLEGAL_CHARACTER?

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