Not one of our installs, but a very good example of a common problem we see on repairs.
First things first. This system will not work in winter, as the bypass-diodes which allow the cells to work independently run horizontal. This means that vertical shading, such as what we cam see here in this photo, will stop the entire panel working. At least they'll get half the year with a working system, and that's better than nothing, but it could have easily been 100%...
Split cell panels, which are fast becoming the industry standard unless you buy off the tv, will allow half the panel to keep working, even with vertical shade. This is particularly useful in solar farms and ground mount systems, many of which often experience shading across the bottom of the panel in winter.
So in summary, if you have a neighbours home which throws shade onto your roof, spend a little more and make sure you go the split cell option!