I believe this is most probably because of a client's Private Feedback [You couldn't know who gave you Bad private feedback + Good public feedback], all you can do now is to try to get more successful contracts to compensate for this over time.
I hope this helps.
I am afraid this is not possible, you will never know who gave you which private feedback because it is "Private".
Also, if you guessed who gave you that bad feedback, I would never recommend that you talk with him about it. Besides that, I don't think that Private feedbacks can be changed.
The best thing you can do now is to care about your next contracts. Fortunately, you have a good and strong profile; all your public reviews are great, you have a nice overview and portfolio. This means that many clients would love to work with you.
Just don't worry much about your JSS, it will increase over time, besides 91% is not bad!
I wish you the best of luck.
Learn more about our awesome Community member Claudia!Learn More
We've added a meeting scheduling tool and an option to sync with your Google or Microsoft calendar to help you streamline interviews and work meetings on Upwork.Learn More
We're releasing a suite of new features for Project Catalog™ designed to help talent promote projects.Learn More
In the webinar, we teach you how to create a project, how to best utilize Project Catalog™ for your independent business, as well as share some best practices and helpful resources.Learn More