I've investigate why one of our UI test is randomly failing all the time:
The reason for this random failure actually turned out to be kind of a bug. The series in the chart needs to be placed more right, if a series picker icon is shown. While this is not the case for the chart on the UI test, there is a chart on the page that is loaded in the background of the popover. As the selector to adjust the placement was global, it also affected the one on the UI test. So the test used to fail depending on the loading speed of the reports in background.
Great find 🥇