A view that hase been running for years selects specific columns from several tables and joins them.
Recently, I added a column to one of the tables, and the vew no longer worked properly.
One of the columns in the query result contained data that was from another column in the table.
I rebuilt the view from a script - no changes to the script - and the problem went away.
The view does not look at the new column.

What is going on?