In All the Mods 7, if you right click on a block that doesn't have a GUI after the reactor has be built, the block detaches and says unknown error. Just seems like you need to add something saying if the block is part of a built reactor multiblock, don't do anything.

Edit: the blocks get fixed after rebuilding the reactor, also discovered that this prevents you from using the reactor control rods

Just built reactor, nothing done:

After right clicking a reactor casing (Notice the error in chat):

another fresh jar, should fix that issue (and similar ones that may have happened if that specific one didn't) https://github.com/BiggerSeries/BiggerReactors/suites/4015229238/artifacts/101403485

Can you try with alpha.5, it has a bunch of random fixes that may have fixed this issue.

This did not fix it. It now crashes the game/server whenever you create a reactor

When you build a reactor and it crashes
crash-2021-10-11_01.21.40-server.txt

When you load into a world with a built reactor:
crash-2021-10-11_01.29.08-server.txt

oh fun, that's a completely different problem
try this jar fresh off CI, should fix that issue, https://github.com/BiggerSeries/Phosphophyllite/suites/4014737692/artifacts/101388250
note: that jar will need forge 37.0.84

Currently working on implementing that. I'll let you know what the result is

That seems to have fixed it! The only other thing that I am noticing is that all of the buttons don't have tool tips but at least the core functions work! You also have to completely rebuild the reactor or a few funky things start happening such as not taking fuel, saying that there is negative RF/T or negative RF in the buffer.

Wait, hold on I just had another issue while trying to get it up and running on my server. Here is the crash log
crash-2021-10-11_06.48.21-server.txt

The game won't even get to the loading screen. Loading ends with an error and this crash log:
crash-2021-10-11_23.00.57-fml.txt

Server seems to be up and running fine

you appear to have a version mismatch there, attempting to load with BiR alpha 5 and Phos alpha 4
you will need both of the new files linked here

Oops. I was trying to follow the updates of ATM 7 and have the new files. Ill just keep my BiR and Phos on alpha 4 until these changes above are implemented into the modpack