So what I experience: board is v3.3 with PCF8563. I let the backup cap get charged fully, and let NTP to sync. I switch off NTP sync, and disconnect power. After some minutes I re-connect power, and the actual time will be the time moment when I disconnected the power. I do not know if ESP saves the time and retrieves it, or the RTC provides this time. Backup voltage is OK. I have replaced the RTC and resonator, same result.