Program Canvas: Contacts stuck on Form Submit step

Hi,

I'm building a program canvas for some data modulation workarounds. One of the steps is a straightforward form submit cloud action, but my contacts get stuck on this step. Clicking the 1 icon and looking at my one contact, it just says 'being processed by app' but the app hasn't done anything for at least 15 minutes.

When I go to the app statistics, there's 0 warnings, 0 errors, 0 success, 1 Total (the one contact that's in there).

Any idea why this might happen? Or is it just that this step takes a really long time to process?

(I removed the contact and re-entered it, hence Total 2 instead of 1).