Error limit in phase calibration - STPM34

Hi, 

We are using the STPM34 in one of our products.

We are facing a problem with phase calibration. Every time we try to execute the calibration process we get an error bigger than (+1) or smaller than (-3). According to the datasheet, the formula of the "theta angle" is arcos((1+e)/2) - 60º, where "e" is the calibration error.

We do not find any reference about error limit...

What should we do when the error will be out of the range (-3) <= e <= (+1)??

We are looking on the item 9.2.2 (page 82).

Tks