Steps to reproduce:
1. select an event
2. From Actions (menu not Action column) Start Task
3. On Tasks tab select a workflow. The correct UI is displayed
4. Now select another workflow, the UI from the next menu item is displayed. You can't select the last workflow either.
The correct workflow UI is shown
Workaround (if any):
Close the action pop-up and reopen, making sure this time you click the correct workflow at the first attempt