Same here. Seems like this is on Esri's end. Just got off the phone with support. They are still trying to figure this out.
Edits:
Just to toss this out there. Support had me try adding "Access-Control-Allow-Origin" to IIS. This actually made the problem a little worse so I removed it.
Also, as others have mentioned, this is almost at random. I have surveys I created back-to-back that are almost identical. Some work. Some don't. Republishing doesn't help either, so the issue is something tied to the surveys.
I published with Connect only. I used 3.13 until today when I updated to 3.14, but no change.
Seems like we need to wait on Esri to publish a fix.