ADS1296R: Chip acquisition waveform and internal voltage reading error

Hello, Ti engineers! My ADS1296R chip has a hardware analog power supply voltage of ± 2.5V and a digital voltage of 3.3V, and the hardware voltage is accurate with a maximum ripple of 46mvpp, using an internal 4V reference source. Now it has been measured that the external VREFP pin is also 4V. When the chip is powered on normally, the MCU reading the internal voltage of the chip is not accurate, with a large deviation. The 2:0 bit of the register CH4SET I set is 011, and the measured voltage is 1.0V, which is incorrect. The actual value should be about 0.82V. But I set the 2:0 bit of register CH3SET to 011, and the measured voltage is correct, which is 0.82V. When connected to the electrocardiogram simulator, the collected waveforms are chaotic and irregular. May I ask what are the reasons for the error? Do you need me to provide any more parameters or schematics? The schematic diagram is almost identical according to the official reference design of ADS1298R.