I would start with a network packet sniffer like wireshark on the server. Sounds like something is clogging the pipes that you want to track down. TCP errors wouldn't point to your server not being powerful enough, it would point to your connection not having enough throughput.
The only other thing I could think of is that the session is somehow expiring prematurely.
Thanks for the advice.
I checked the admin console when I encountered this issue. The connection was still on and I could refresh the browser to bring back the previous screen and continued to work in the system.
I believe the session is still on. The frustration is all my uncommitted data before the error would be gone.
Will forward your suggestion to my network team though.
Just an update.
We have the solution, but I am not exactly sure how to solve it.
According to our network staff, it is the reverse proxy issue.
Just to give a clue to those who face the same issue.