Some of the options available to perform the bypass before the proxy are the following:
After applying one of the options above, the traffic will go directly from the workstation to the Firewall or upstream device in the local environment. Make sure to have said device configured to accept this traffic, as in most of the Explicit environments the upstream is set up in a way that rejects all sources but the Proxy's IP.
Have in mind that the traffic may take a different physical route in your environment, thus if a problem in the upstream is suspected, this may skip the problematic device entirely, making it look like the proxy is at fault when it's in fact something else on the network. Verify the network path being followed with a tracert / traceroute from the client to make sure that all the same devices (but the proxy) are matched.