We have solutions we want to share with you. Please try each of them.
- Set the fixed browser size: WebUI.setViewPortSize(1920, 1080), for example, before running
You can use this site to get your current screen size
- Check your Default Smart Wait status (Project Settings -> Execution). Please turn it off if the current status is on and vice versa
- Review the steps if there is a need to add the Wait keywords
- Update the headless browser to the latest version
- Execute the test on IE, Chrome and Firefox headless and compare the results