When looking for second-hand panels, you have to accept beforehand that
they are likely to be damaged. Some defects are easy to identify, others can be revealed only with the help of an expert or special equipment. For example, a broken junction box is self-evident, but microcracks can't always be found with the naked eye.
The damage to a PV module isn't always critical, but can be troublesome nonetheless: the output of a solar panel drops and, in some cases, the lifetime of a module decreases. Some problems you can fix yourself if you are up for it – for example, replacing a broken bypass diode is rather simple. However, sometimes it is not just worth it. Moreover, if you've bought damaged panels from someone, getting warranty support for them is usually a pipe dream. So, while purchasing old PV modules might save you money, it's a risky move overall.