W115 side marker light removal

[j-galap]

Hi folks,

One of my side markers is causing some shorting out and blowing one of the fuses on my '74 240D.



Taking the lens out is of course a ten second job but inside the trunk has been stubborn so I want to ensure I don't break anything!



There's the two 7mm nuts to take out (done - ten seconds each again) but it's the rubber cover for the electrical connection that doesn't want to budge easily. It's reassuringly tight on there! Is there a trick to getting it out without damaging anything?

Thanks