With my MPPT 100/50, after a year of no problems, I'm experiencing battery voltage dropping to almost just 10 volts, causing my invertor to kick off. Haven't changed my usage patterns or increased loads. These drops occur mostly but not always after the solar ends as the sun sets. The battery SOC is always above 60% but below 70%. I have 3 100 Ah Lipo batteries. My battery voltage and solar power charts are attached. Any ideas?