"Stage has open output streams" while it is connected...

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Hello, I try to do the following pipeline:

• query a rest API with a "problem" to solve, which can take some time so it is asynchronous: it returns an ID, which then I use later
• query in loop a rest API with the ID to get the status of the job, until the status is SOLVED
• then query the rest API to get the solution for that job.

The error is on the Stream Selector, although the "2" output is connected to the previous "HTTP client (/jobs)", the stream is not very visible (in blue)...

I don't understand this error, or maybe this is not the good way to do a loop ? Thanks !