If you excluded hardware issues (search FAQs for “charging”) and battery level indicator issues (search FAQs for “battery level”) and your CI Pad battery level still goes below 50% regularly, there might be a software glitch in the charging service.
Here is a video guide, how to fix it.
Alternatively, just turn off AI Charge on the Power&Charge tab in the Carpe Manager app and restart CI Pad. After connecting it to a power source and disconnecting it again, the charging will go back to stock settings and there will no longer be any cycles and advanced battery management. It will simply just charge when connected to power and discharge when not. The batteries on CI Pads rarely ever fail, so letting it charge to 100% is a good trade-off for not having sleepless nights about charging algorithms;-).
And what is more important – there is an Android 11 update that changes everything about charging and solves most issues. Please consider updating.