Error with Stories I have Split in two

On Product Backlog page
I split a Story in two
I click on "Themes" in any of the splitted Stories
I get the following message from Kunagi:
<<
Unexpected Error
JavaScriptException: (TypeError)
__gwt$exception: <skipped>: GL(...) is null
Reload
>>
Clicking on "reload" brings me to ":8082/kunagi/#projectSelector" with a closed project
I can work on Stories fine, even the one giving me the error.