This bug is in the discussion forums and reported by Joseph Rézeau

Moodle 4.0.2

https://moodle.org/mod/forum/discuss.php?d=436367

I've independently found this same bug using these same steps on Moodle 4.0.4.

To reproduce this bug:

1. Create two quiz activities inside a course
2. Create and set the first quiz settings to: 
   • Set Grade to any number except 0
   • Under Review Options, uncheck 'Marks' under 'Later, while the quiz is still open'
   • Add Activity Completion: Check both 'Require grade'
     • Student must receive a grade to complete this activity
     • Student must receive a passing grade to complete this activity
   • Add questions so you can test the quiz to pass/fail
3. Create and set the second quiz settings to:
   • Under Review Options, uncheck 'Marks' under 'Later, while the quiz is still open'
   • Under Restrict Access, Add a restriction for activity completion, set it to the first quiz and set 'Must be complete with pass grade'
4. Once you have both quizzes set, the second quiz should show 'Restricted until first quiz is complete'
5. Now, go to the first quiz and try to fail the quiz. 
6. If you go back to the course, the second quiz will be unlocked and this is the bug, because it is supposed to not pass the first quiz.

But if you have 'Marks' under 'Later, while the quiz is still open' set up on the quizzes, they will work properly.

I work on a team of Moodle developers, and we would like to help if we can to resolve this bug quickly. Any information about how we can fix this bug would be appreciated, and we'd share any patches we create with the community.