There is something weird going on with DimDoors, when I go into a door, my server starts loading all the planets I have from Advanced Rocketry. I'm not sure whats going on here but below is my server log, you can find the start of the problem if you control+F the phrase "RiP Server"

https://puu.sh/B3eRS/7ba926dcba.log

Well, I can agree with this comment:
https://github.com/DimensionalDevelopment/DimDoors/blob/1.12-WIP/src/main/java/org/dimdev/dimdoors/shared/rifts/registry/RiftRegistry.java#L164

Looks like half a SingleTon Instance implementation. It's supposed to load all dimensions once in order to create a Rift Registry for all of it together, but it shouldn't do this every time a player changes dimension.

I'll talk it over with @Runemoro and we'll see what we can do. Thank you for the report. :)

We did some rough testing and from what I can see it would do it once every server restart to the first person who went into a dimdoor.