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Considering you have "Structural Solutions" and "More Decorations" I am making a guess that this may cause a ReliableBuffer overflow (from too many recipes and schematics added by the decoration mods) -> you can try and disable these two and see if it works
Well for now it's only "fix" is removing mods that add a lot of content until it works again. As far as I know they are working on an actual solution, but it's very complicated, so there is no ETA as of now.
True, extra milestones adds a lot (if that mod is what you mean) but right now it adds around ~280 recipes and schematics if its mod page is to be believed. (+the few things its dependencies add) Structural solutions adds ~480 recipes alone so its not even a contest.