Reminders app on iOS loses images

When I attach an image from my image library to a reminder, it will persist for days or weeks and then stop displaying the thumbnail. When it goes away, a blank spot is shown where the image should be. If I tap on the spot where the thumbnail should be, the full size image displays. My iOS is current. The app is updated. I have restarted my phone. If I delete the reminder and recreate it, the same thing happens again. Screenshot is attached