Hello,
I'm trying to build a new reactor ( 967 ) on my ATM7 server, the structure is detected as invalid and the An unknown multiblock error has occurred, report to mod author error appears.
Any ideas ?
Screens available bellows

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biggerreactors-1.18.1-0.6.0-beta.jar

What mod version?

Phos 0.6.0-beta.0.1 had some multiblock related fixes in it, which may fix your issue

I've just rebuild a 7x7x7, on click on the terminal, dimensions are retrieved as 1x1x1

likely fixed by BiggerSeries/Phosphophyllite@db9b88d if not fixed earlier in beta.0.1, ive also been unable to reproduce this specific issue, so, ill be closing it