It's only a display issue - the starred status is, in fact, correctly stored.
Steps to replicate the issue :
- As a mentor go to Special:MentorDashboard (testwiki wmf.28)
- Mark any of your mentees as starred (click on a star at a mentee's user name) - the star becomes black. A mentee is starred.
- Perform any sorting on the columns - the star will become non-black.
- Open Filters and select the option "Only show starred mentees" - the mentee that you just starred will be display, but the star is displayed as non-black.
What should have happened instead?:
- Once a mentee is starred (the star is clicked), the status of the star should stay as marked. It should not change with any sorting or filter options.
Other information (browser name/version, screenshots, etc.):
- it could be confusing to a user who doesn't see whether the starred status is saved.
- the animated gif below shows
- two mentees were starred
- Filters' option - "Only show starred mentees" was applied
- two starred mentees are shown with the stars displayed as non-black.