This "may" be happening between your computer and the TBN server, so can't be fixed at either end.
Copied from the internet:
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HTTP Error 502 Bad gateway
A server is acting as a gateway or proxy to fulfil the request by the client (e.g. your Web browser) to access the requested URL. This server received an invalid response from an upstream server it accessed to fulfil the request.
This usually does not mean that the upstream server is down (no response to the gateway/proxy), but rather that the upstream server and the gateway/proxy do not agree on the protocol for exchanging data. Given that Internet protocols are quite clear, it often means that one or both machines have been incorrectly or incompletely programmed.