Answer
Once a Lobby Data Source is pointed at an IAL rather than directly at a base table/view, EVERY column referenced anywhere in that Data Source, including columns used only in filter conditions and not shown as output columns, must genuinely exist as a real column in that IAL itself. Unlike querying a standard base table/view directly, where you aren't restricted to any predefined column set, an IAL-based Data Source can only reference exactly the columns the IAL actually exposes in its own SELECT list — so any condition or output column referencing a field not present in the IAL fails. The fix is adding every needed column to the IAL's own definition, rather than assuming a Lobby Data Source built on an IAL can freely reference the original underlying tables' full column set the way querying those tables directly would allow.