Some solar panels are assembled by hand and some by machine, does it make a difference?
When a solar panel is being assembled and prepared for lamination it is crucial that no dirt, solder, dust, hair or other foreign particles are caught or they can cause bubbles in the laminate or air gaps which can lead to premature failure. Strictly clean conditions are essential in manufacturing solar panels. LG panels for example are made in semi conductor environments, to remove dust from the environments.
The alignment of solar cells is also an important indicator of workmanship in a solar panel. Poorly aligned solar cells can introduce stress into the interconnections or the potential for current leakage between cells.
When you are assessing a solar panel, check that there are no inclusions accidentally laminated under the glass and that the solar cells are perfectly aligned as this will affect the output of the system.