Water ingress rear wheel arch/lights

[Kat5555]

Hi all. I have water coming into the boot from either rear wheel arch, rear lights or both. This is causing probs with the lights, warning for rear brake out and left indicator. Had a mechanic look over it and puddle of water below electrics, corrosion to the sam’s and he’s suggesting new sams and new light units/ re seal them.
Has anyone had any luck permanently fixing this, stopping the water coming in or getting Mercedes dealer to recognise this is a common fault? Mines a 2007 model

 

[ash59fifty-uk]

2007 model of what?

Cars have internal guttering so to speak, water run offs so it’s possible one of these may be blocked and need unclogging

 

[Kat5555]

Mercedes ml. Apparently it’s a common problem