Welcome to the forum. I've not owned this model jazz or had this leak . But I have done bodywork on classic cars.
Its possible that the left light fittings/ trim has been removed and not replaced properly. A slight discrepancy with clipping/bolting at one end of the fitting can multiply the angle for a larger gap at another point.
But it may be due to an impact at the rear left side , which could have been quite slight . Possibly just confined to the flexible rear bumper shifting slightly where its bolted to the metal bodywork. But it might be that the underlying metal bodywork has been distorted. :'(
I would try to precision measure the vertical relationship between the lower and upper bolts on your first photo . Perhaps run a plumb line down ,or suitable spirit level/laser line, passing through the centre line of the lower bolt and then precision measure how far this line is to the right of the upper bolt , Then compare this with the same results from the right side. This may show that the upper bolts threaded hole has been pushed towards the centre of the car. But wouldnt show if both the upper and lower bolts have been displaced by the same amount. If you suspect this try comparing left and right bolt distances to the centre line of the car. The easiest way is to measure to the boot lock strike bar, but this is adjustable by a few millimeters so I wouldnt undertake any expensive repairs without double checking.
If you suspect the problem is limited to the flexible rear bumper and the underlying metalwork is undamaged you could try loosening the fixing bolt(s) to see if the bumper starts to ping back into better shape. . But a word of warning,if you remove the bolt entirely and it transpires the underlying metalwork has indeed moved the bumper might ping back into shape with its bolt hole no longer aligning with the threaded hole .. Which will complicate matters. But hopefully by just loosening the bolt (s) you will be able judge if this is happening in time to stop and rethink whether to continue.
Sorry, I realise any suggestion of impact damage will be unwelcome. It could have happened in a car park without leaving any visible evidence. The previous owner (or you) may not have been aware it had happened. But its not likely to be sufficent damage to make the car unsafe in anyway (other than the leak) so the option remains to make more practical repairs that are not 'like new'.
If bodywork distortion is suspected the safest answer is to consult a bodyshop. . But I have realigned bodywork myself in the past where there were are no monocoque structural strength issues (including a dented boot shut.) Pushing (or pulling ) it back into place using a car jack and baulks of timber suitably braced can work well . (Pro bodyshops use hydraulic rams for the same job, )