Please find the below steps to replicate the issue :
If you close and re-open flow / or save it seems to work
This issue we are facing in ARD Version 188.8.131.52.
Release : 3.1
Component : CA Agile Requirements Designer
This issue has been addressed in the upcoming 3.1 patch. Before its release, there is a simple workaround: select (click) one of the paths in the list before saving. Confirmed fixed in ARD patch 184.108.40.206