Stop inactive Users causing 'Errrors' in Risk Register

We have had several instances where an 'Encountered Error' message is displayed when trying to access items in the Risk Register. It has then transpired that an Inactive User is named in the Risk and therefore seems to stop anyone else opening it. If we temporarily reactive the user, access then works and the Safety Manager has to check/amend names involved in said risk. Is there anyway this anomaly can be rectified?