Thank you for posting the issue. These issues with the Builder integration and EyeLink were brought to our attention last week by another user. Basically the issue is that EyeLink start / stop record calls can take up to 0.5 seconds to run and we did not factor this into the design of the ETRecord functionality. Other supported trackers do not have this issue.
There is no immediate fix for the problem, so currently you can use the Builder interface to configure and calibrate the EyeLink, but can not use the ETRecord or ROI features.
Instead you will need to add custom code to the project where you want to start or stop recording by adding custom code components. To start recording add a new routine and then add the following to the begin routine tab of a custom code component in the routine:
eyetracker.setRecordingState(True)
To stop recording add a new routine and then add the following to the end routine tab of a custom code component:
eyetracker.setRecordingState(False)
Starting and stopping of recording should be done when no keyboard events are expected so if one occurs during that 0.5 second time period it is not dropped.
A proper fix for this will be available in the a future release. Sorry for any inconvience.