krypton VS DimensionalThreading

Starlight performs substantially better than phosphor and greatly speeds up terrain generation. Krypton for networking performance. C2ME or tic-tacs (both aim to do the same thing and are not mutually compatible) greatly improve world loading and terrain generation but are experimental and, in my experience, not compatible with a lot of other mods. Dimensional Threading puts each dimension on a separate thread, but also tends to not be very compatible with other mods. FerriteCore aims to reduce ram usage. This page has a whole list of mods.

Krypton ( astei/krypton )

I would recommend a fabric server running krypton, lithium, starlight, tic-tacs, hydrogen, and ferritecore. Those mods are geared towards optimizing chunk generation and loading while having 0 impact on vanilla game behavior (the last two are geared for reducing ram usage). Of all the performance mods I've messed around with, those are the ones that I would recommend most. You could also add carpet and set it up to add tps to the tab list if you want to easily see that number.

The Dimensional Threading mod offers this on 1.16+ fabric servers

You don't need to redesign the server. You can just use these mods.

Dimthreads may cause some issues, though seemingly none that are similar to yours https://github.com/WearBlackAllDay/DimensionalThreading/issues. Also make sure you configured it to use more than 3 threads since you have additional dimension mods (Aether);

Starlight performs substantially better than phosphor and greatly speeds up terrain generation. Krypton for networking performance. C2ME or tic-tacs (both aim to do the same thing and are not mutually compatible) greatly improve world loading and terrain generation but are experimental and, in my experience, not compatible with a lot of other mods. Dimensional Threading puts each dimension on a separate thread, but also tends to not be very compatible with other mods. FerriteCore aims to reduce ram usage. This page has a whole list of mods.

(Experimental) Dimensional Threading ( WearBlackAllDay/DimensionalThreading )

SOLVED: Thanks for the suggestion! I just figured out the problem. I had the experimental mod called Dimensional Threading installed on the server https://github.com/WearBlackAllDay/DimensionalThreading.