Solar Pathlight Inaccurate Battery Levels?

I have four solar pathlights, one of which has a battery that drains quickly and I have to bring it in every 3-4 days to charge. Last weekend, it took over 24 hours for the battery to go from 0 to 80%, then after unplugging it it soon went up to near 100%. I charged it overnight Sunday and it went offline while plugged in. I moved it and plugged it in, and it started over at 0% and it took nearly 12 hours just to get it to 25%, but after unplugging, it again jumped up to 80%.I have two more lights that turned off without warning. The app still showed the lights are on and they were online. I plugged them in and their battery levels immediately dropped from 40% to 0%. They are also charging slower than normal.Overnight, another light went offline without warning. The battery was around 40% but when I plugged it in to get it back online, the battery level again went to 0%.