Oh, you are using a PCEye Go eye tracker, not PCEye Explore eye tracker? Sorry for not spotting the mix-up earlier.
I would not expect the PCEye Go interaction software to work simultaneously with the EyeX Engine running on the device. The two run times will both try to handle the screen setup and calibration of the eye tracker. I guess it might be quite random which setup is stored in the eye tracker when using different eye tracking software. Depending on how the PCEye Go is mounted on the tablet, the EyeX Engine screen setup might end up with an incorrect screen plane (it assumes the eye tracker is mounted in a specific way).
I have noticed that Tobii is a quite hardware-centric company still. When someone says that a certain Tobii eye tracker is compatible with Tobii EyeX, they quite literary mean the physical eye tracker and its drivers, but not all of the associated interaction software.