Sometimes, after working on issues, the modal window actions stop working.
When that is the case, clicking actions such as "Plan", "Assign", "Confirm", etc. will have no effect.
To fix it, the whole page needs to be reloaded.
Here are the steps to reproduce:
1) Go to the open issues page
2) Pick any issue
3) Click "Plan", leave the current action plan and click on the "Plan" button
4) Click "Assign to me"
5) Click "Assign", select "Unassigned" and click on the "Assign" button
All actions should be broken from there (except the "Close" button, which also stops to work under some condition)
Note that simply assigning to self and unassigning over and over eventually also breaks all actions.