MSP430FR5994: Internal Temperature Sensor problem

Part Number: MSP430FR5994

Hi,

I'm using the internal temperature sensor of the MSP430FR5994 and I'm facing the issue below.

When measuring the temperature at room temperature (approximately 25°C) and calculate using CAL_ADC_12T30 and CAL_ADC_12T85,
most of samples have a correct temperature of around 25°C,
although some samples yield around 0°C or 7°C temperature (abnormal).
What are the possible causes?
And, how can I solve it?

Reference Voltage is 1.2V,
I am using the formula of
temperatureDegC = (float)(((float)val - CALADC12_12V_30) * (85 - 30)) /
(CALADC12_12V_85 - CALADC12_12V_30) + 30.0f;
for calculation.

The data when measured in room temperature about 25°C are as follows.

Thanks in advance.