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I currently could not reproduced the issue yet on my end.
When I test submitted your jotform http://form.jotformpro.com/form/41758248099973 it was able to proceed to the Thank You page just fine after submission.
From the look on your screenshot
I can see that you have uploaded a file for the submission.
You need to wait for the upload to be completed, before the form will move on to the Thank You page.
Hope this help. Please let us know if the issue persist.