Hi @kees_van_2727, thanks for reaching out! We're sorry about the trouble.
Please let us know the version of Photoshop you're working on, along with your computer's operating system. What's the format of the file you're working on?
Please let us know the options you've selected at the bar at the top.
Thanks for sharing the screenshot again! The marks are visible in the original image you shared as well. It would be helpful to see the settings you're using to apply the Remove tool.
Can you create a small video of the workflow and share it with us?