Made another post more complex about the profile on upwork but no one responded so I will try now to address only this issue.
No one knows all the factors that go into the JSS score. The best thing for you to do now is just concentrate and delivering great results to clients and it will come back up.
It looks like you had a few jobs that ended more than 6 months ago. Therefore, the better of your 6-month and 12-month scores will be displayed on your profile and if a good feedback falls off a calculation, it may cause a drop in your score. We won't be able to share which contract in particular affected your score in what way, but you can check out this help article to learn about all the factors that go into the calculation.