A friend and I have been playing a multiplayer game of Space Age on a server hosted at Nodecraft.io. We have been leaving the server running overnight, and when we returned today, we had a massive lag spike. After downloading and running the save locally, we found that that did not improve our performance at all; if anything, it dropped both fps and ups even further. I know my computer isn't being bottlenecked, as the GPU and CPU usage never exceeded 20% (I run an AMD Ryzen 9 5900X and an NVidia RTX 3080).
The performance problems only began after we arrived at Fulgora.
Here is a screenshot of show-time-usage and show-entity-time-usage:

Here is the Log File: Here is the most recent Save File: Here is the exported performance data: