Hi Jill! Thank you for flagging this behavior for us. I've done a bit of digging into this behavior and it sounds like a match for a bug that our team is presently working to resolve. Presently reproducible with interface-only users in the list layout, if a previously visible field is deleted, this error can appear. We're hoping to have a permanent fix for this out in the upcoming week, though in the interim, re-adding a layout routinely resolves this, as you've found. Let me know if this gives you any further trouble and I'm happy to take a closer look with you.