/headers Endpoint doesn't show all request headers

[jackiecan]

Hi, I tried to verify the usage of the X-Forwarded-For and Via-Header of my squid proxy with the /headers Endpoint which "Return the incoming request's HTTP headers." But the headers weren't present in the servers response like I would expect it.
So I tested my proxy with a simple Python Webserver which indeed showed the presence of both headers. Is there some sort of preprocessing (maybe while Loadbalancing etc.) that removes headers? If so, maybe at least a notice of the possible removing of headers would be nice.