0 Error decoding JSON data: Syntax error (when uploading profile image)

I'm not sure what's happened while I was testing the profile image upload, but one test user I have set up throws the above error when I try to login.

The only thing I can think of was that I was uploading an image file that was the same name as the previous one that was loaded - Could this be a cause?

Other user logins seem ok - It's just this one user.

Known issue caused by Joomlas user params column being double JSON encoded. See the below regarding this.

www.joomlapolis.com/forum/153-professional-member-support/235097-solved-0-error-decoding-json-data-syntax-error?start=12#295786

www.joomlapolis.com/forum/147-potential-bug/236745-wrong-params-value-after-frontend-profile-editing?start=6#294554

You will need to reset the params column on your _users database table as shown below.

www.joomlapolis.com/forum/153-professional-member-support/235097-solved-0-error-decoding-json-data-syntax-error?start=6#287431

Then ensure the params field within CB > Field Management is set to always display in profile edit since we've a workaround for Joomla doing that. We have to move the workaround to happen sooner than field save processing, but until then you need to keep the field accessible for the workaround to work.