When I open the page in 2 different browsers the one that opened it first throws the error mentioned in the title.
This happens since 1.3.42 this was a Development build so I did not pay much attention.
Now however the error is in the release.
My Testcase has Firefox opening it first then Chrome.
The only reason it could happen is if the application somehow is trying to create the DragDrop component twice. I tried to create the error and the only way to get close to it is to create a new instance of the Wisej.Web.Application class. I don’t know why the constructor is public, it shouldn’t be.
Can you check if your app creates a new Wisej.Web.Application() somewhere?