No root cause yet…. I'll be sure to post any findings / resolution on this thread. I had Curtis from Quest actually walk through via screenshare step-by-step the configuration of the listform and the parent/child fields, and we both ended-up scratching our heads. Other auto-fill fields work fine, cross-list lookups, etc. But in this case I have a form in one list (A), a field (parent) configured as a cross-site lookup from a second list (B), and a field (consumer) performing a cross-site lookup to a "third" list (C). If I set the consumer field to be a simple cross-site lookup, it works no problem. But what I need it to do is filter based on the parent field lookup value, after an auto-post refreshes the form. What actually happens is after the auto-post refresh the consumer field (C) doesn't contain any values, is simply blank with a flashing cursor in it.
I'll update as I learn more!