We are facing the same issue, but for us behavior is, it works fine on our DEV server and does not work on local somehow

My observation and debugging shows that, if you have used <Link  of JSS and if you are using `{editable:true}` that is causing the issue for us

if I make it `{editable:false}` my experience editor loads and I am able to edit other parts

Currently with `{editable:true}` I am not even able to see Add Here button but with `{editable:false}` I am able to.