I don't think SANS10142 allows you to link the neutrals like that (I am not a sparky, but I do a lot of support from the software side). If I read that part correctly, you are allowed a common neutral only in some cases (it is in Annex S I think, with the diagrams about generator/alternate supply connections). Other parts of the world do allow it. I agree that often you get an erroneous error 8 indicating that the relay was closed (PE2 closed) because of bad devices in the house. Typically cheap surge arrestors and EMI filtering, which typically contains a capacitive component that passes current at some frequencies but not at 50Hz. Also, the issue is mostly resolved after late 2020/early 2021. An auxiliary contact on the bonding relay is used for the test now instead of a voltage measurement. I had one case where the customer got a "PE2 open" error. If you get that one, you are probably looking at a real failure. However, this customer discovered it is caused by a long unused PV cable going up to the roof (nothing connected, future expansion), acting like a big old AM radio antenna. He disconnected that and the problem went away.
