502 Bad Gateway
A web service has misconfigured its host and port.
Bind your host to 0.0.0.0 and optionally set the PORT environment variable to use a custom port (the default port is 10000).
A newly added custom domain is not yet redirecting to its web service.
In most cases this resolves within a few minutes, but it might take up to an hour.
A Node.js web service is experiencing intermittent timeouts or Connection reset by peer errors. Try increasing the values for server.keepAliveTimeout and server.headersTimeout (such as to 120000 for 120 seconds).
A service is experiencing WORKER, SIGKILL, or SIGTERM warnings (e.g., [CRITICAL] WORKER TIMEOUT).
Consider increasing your timeout values and worker limits (e.g., via the gunicorn timeout parameter).