With the recent Tobii Eye Tracker 5 firmware update (thanks u/CaptainSnackbar - link in comments), I think I've gotten my setup nice and stable with help from u/funnybuttnoises. Feel free to try
EyeTracking Glasses
Next gen tracking? Tobii Eye Tracker 5 review part one: Unboxing and setup – Stormbirds
What is eye tracking? - Tobii Dynavox US
Tobii Eye Tracker 5 | Next Generation of Head and Eye Tracking