Adafruit MPRLS Pressure Sensor - Readings that drift

I have an MPRLS breakout, connected to a raspberry pi.

the pressure reading worked as expected initially showing a value of ~1000hPa at ambient pressure. The reading was stable at this level for 5-10min.

I drew a vacuum on the pressure port which took the reading down to ~300hPa,
however upon releasing the vacuum the pressure increased to 400hPa and is now, slowly, (1hPa per couple of seconds) increasing.

Drawing a vacuum again resulted in readings below 0hPa…

Is this a hardware fault? (maybe an issue with the sealing of the vacuum reference)
Or is there some internal averaging that the sensor does in the background to self calibrate?

The program used:

import time
import board
import busio
import adafruit_mprls

i2c = busio.I2C(board.SCL, board.SDA)
mpr = adafruit_mprls.MPRLS(i2c, psi_min=0, psi_max=25)

print("Imports Successful")

while True:

    	print(round(mpr.pressure, 2))

    	print("loop failed")