Love it when you thought your biconjugate gradient solver was actually converging compared to deflated conjugate gradient but the whole point of it was that previous people coded the following:

// Read solver for V
            word solverV
            (
                mesh.solutionDict().solver(V.name()).lookup("solver")
            );

            if(solverV != "deflatedPCG")
            {
// TODO: Read reference values
//                 VEqn.setReference(VRefCell, VRefValue);
                VEqn.setReference(0, 0.0);
            }`

Which doesnt make physical sense, I do get it when you have

p_rgh

but there is not real reference for it. So I commented it out ran the biconjugate gradient again and no convergence... But some interesting insights