I cannot replicate your Issue, what exactly are you doing to make the Reactor update its outsides? Because that is what would need to happen in order for your symptoms to be the case. Are you somehow cycling Coolant between reactor blocks or so and one of them ends up empty, flickering the whole Setup?
Edit: I DID find something weird in the Fluid Tank Update Code, so it MIGHT be that.
Edit Again: I did find yet another Issue, but it might be fixed now.