I might setup Wireshark along the way to see if I'm getting errors while looking at logs.  But Wireshark can often give you more truth about networking issues.

(Trace Agent to OCM...OCM to Internet Proxy/Internet)

Possibly the OCM is overloaded and rejecting incoming requests if you have many devices.  Perhaps the Internet Proxy Server is refusing lots of requests from the OCM.

While one may quibble over retry amounts if you are failing that often it could be overwhelming retry requests.  I may also maybe trace pulling large files from the OCM down and see if I'm getting many lost packets and retries.

I sounds like some type of networking issue.

I have seen some Internet Proxy devices get overwhelmed when unintended local traffic gets routed through them.  Imagine if a device pulls down a 2gb bundle from a local ZENworks primary, but the HTTPS request flows through the Internet Proxy Server and then 1,000 devices all do that.....

I have seen such things when there were missing exclusions or logic errors in how various proxies are configured on the agent.  And of course it would not have to just be ZCM that does this, but ZCM does do HTTPS traffic, so it could get caught up in a Non-ZENworks proxy.