I eventually got ot the lights and changed both side lights as the error said "Sidelamps faulty" but it's still the same. I even gave the connectors a clean with contact spray but I still got the error.
Thing is , the lights all work fine so ... for now
Check the plugs onto the actual tail lamp unit. 407's have a habit of burning the ground connection pin, might have the same problem with yours.
Also, these sensing circuits are quite particular about resistance/power draw. Have had a lot of issues, particularly in BMW's, where cheap bulbs have a resistance/power draw outside of what is expected, so, even though the bulb lights up, it triggers the bulb out warning.