Beetle esp32 c6 mini I2C didnt work on battery

      When I first got the board, I²C (SDA/SCL) worked on battery power, but now it only works when connected by USB. The setup uses a Sensirion SEN66, W25Q64, and a DS3231 RTC. Battery voltage measures 3.7–4.1 V, so that likely isn’t the issue. I’d like to understand possible causes before buying a new board. 
      Before adding the RTC and flash modules, the board worked normally. After the issue appeared, I suspected the RTC might be the cause. If that’s true, how can I keep using it without running into this problem again?