Have same issue but playing 1.20.1 on forge 47.2.21
RftoolsPower version is 1.20-6.0.1
I don't have rubidium, I have Embeddium and Embeddium extras which are pretty much a clone of it
If anyone figures out a setting to solve that issue, let me know please, I need theses mods cause of shaders in ATM9 No Frills pack.

Version?

apologies totally forgot to add it. RFTools Power 1.19-5.1.1

And on what MC version are you playing this? 1.19.2 or 1.19.3

1.19.2

i have them all minus Canary as of now

Got similar issue after installing few optimisation mods along with broken detection of old dimensions from rftools dimensions (new ones work well). Do you have any optimisation mods from a list down below installed?

Minecraft v 1.19.2, Forge v 43.2.4, RFTools Power v 5.0.3, Dimensions v 9.0.3, Base v 4.0.3, lib v 7.0.7.

Haven't upgraded them because it caused issues with old dimensions and missing planet icon over dimension builder.
[UPD: Not an issue anymore.]

[UPD: After updating mcjtylib and all other mods that use it to the latest version problem remains the same.

Checking level.dat through NBTExplorer revealed that only the newest world folders remained (after including opt mods).]

Optimisation mods installed (lib included):
Rubidium v0.6.2
Oculus v1.2.8a
Clumps v9.0.0+14
Canary v0.1.8
FastFurnace v7.0.0
FastSuite v4.0.0
FastWorkbench v7.0.1
Saturn v0.0.1
Smoothboot(reloaded) v0.0.2
Placebo 7.1.2

I'm sure one of them causing the issue, I just can't tell which ATM.

Found out that Rubidium causes it. Not sure if it can be solved through changing config yet.