I haven’t read all the previous post but I can share my experience with the same error so it may help someone
I noticed the error ‘Callback failed: the server did not respond’ when trying to run this logic:
Output Foo:
Input1 Foo -> refresh the page using javascript
Input2 Foo -> call another callback
It seems like refreshing the page while another callback is called would prompt the error
I fixed it by removing the second input because anyway I wanted the Output Foo to refresh the page