FINALLY figured it out! This was a though one because I wasn’t able to find “the one module” that was causing it. It turned out to be two modules that had to be enabled together.
Specifically, the problem is the Compendium Browser. When you have it enabled, it will use up a lot of RAM, but when you have it enabled along with your Shared compendium, that will cause the server RAM to spike to 600MB/900MB when the page loads. I think the module on load will flood the server with requests to load every compendium and serve its data, which is bad in every aspect because it’s flooding the network, forcing the server to unnecessarily read files it doesn’t need, process them and load them in RAM, and it puts strain on the client side’s RAM as well.
It seems that it wasn’t that big of a deal for most compendiums, but when you enable your shared compendium module which had 75MB of compendium data in it, that’s where things got bad.
Note that your new copy of the world also has thos emodules enabled, and I just tried loading it, and it got to 950MB of server RAM used, so you’ll have the same problem potentially.