These smaller solar panels are great for people starting with solar power, as they are inexpensive, and, at first glance, seem to be weather proof. Well the connections on back are not weather proof and over time in the sun, the epoxy turns cloudy and reduces the power the panel will produce. There is a clear UV resistant epoxy but it's expensive and Chinese coated panels will use only the cheapest epoxy available.
One option is to use this thin silicone coating: https://smile.amazon.com/dp/B008O9YIV6/?coliid=I3VTXHSO4A9HUL&colid=2ZLX7ZSONBOBS&psc=1&ref_=lv_ov_lig_dp_it
I generally use 100% silicone to make things weatherproof. But I use the smaller tubes because the big tubes, once opened, go bad in about 6-8 months.