matt85

I'm suspecting I'm making a rookie mistake here but not sure which.
Got approved for Global Entry a month ago, have been using TSA Pre extensively since then so I know it's active. Now I had my first entry from an international flight and used the Global Entry kiosk.
I'm a non-US citizen, and the lady at the interview told me to scan my visa, not my passport info page. Did that, and I could see my visa #, name and other info popping up at the kiosk.
Then it proceeded to taking the picture, so I saw the camera view. But seconds later, the kiosk shows that there was an error with my travel document and I should proceed to a passport agent.
I tried it three times with the same result, and somebody was using this kiosk before me successfully, so I don't think the machine was broken.
The agent processed me normally, meaning I had to fill out the paper customs form and all. That's of course not ideal given that I'm GE member.
what confuses me is that the document data showed up fine first, before seconds later erroring out.

Any idea what's the cause of this?

Thanks!