Did you read the help file in SiTechExe/Config/ChangeConfig/Encoders?

Here's the snippet about precise mode:

2. Precise Mode:  
If selected, then as soon as there is a dis-agreement between the motor location and the encoder location that exceeds the Supervisory Threshold,  then the motor location is updated to the encoder location, and the scope will re-center.  Use the Precise mode if you have the low resolution encoders, but you're not doing photography (the "Precise" word is used loosely!).

Make sure that you set up the "Supervisory Threshold" to have a value of about 1.5 to 2 times the resolution of the encoder.
As an example, if you have 10,000 tick (2500 line) USDigital encoders, then you have about 2 arc minute resolution.  You should set up your "Supervisory Threshold to at least 3 arc minutes.