See this Discuss thread created by Ann Campbell: https://discuss.sonarsource.com/t/weird-wrong-overlapping-flow/1796. The user experience is very poor as the user cannot step through the list of locations and see the relevant code at each step.
Unfortunately, the issue in the thread has been closed so that UI issue is now being shown differently. It appears that that the problem is caused by overlapping locations.
I confirm the problem is on the UI part. It's possible to have in the execution flow multiple times the same location at different execution steps.
In this example, step 5-9 and 2-4 are at the same lines.