After crappy workmanship, it's the single biggest problem with solar! It's also the reason why cheap inverters do not work. Yes, cheap inverters also have additional issues a lot of the time, with cheaper components in some cases. However, the software inside them also doesn't allow them to tolerate higher voltages on the grid, leading to constant drop outs like in the photo below.
This is taken from a sungrow inverter that we have been back to once already to fix the issue, and it is not ours, nor the inverters, it's the grids fault for not performing as it should.
The end result of this is we have to prepare a report so the grid owner, which in this case is energex, can come and adjust the voltage in the street. Notice how it's working fine then suddenly cuts out for 10 mins? That's the inverter protecting itself from all the extra power!
FYI, most of our fix up jobs these days and people who brought cheap systems and now can't get help from the company they brought through. It's a tricky one, as technically it's not technically the companies fault, both the retailer and the manufacturer, that this is occurring, so it's from the goodness of our heart that we do it for our customers.
Tricky yes, but easy to avoid if you stick to at least a decent quality system and a company who cares.