Here's what happened: I added a column to a source table, went into the Data Flow source, refreshed the table list, selected the table, and checked all the output columns that I wanted. Then I resolved all the naming issues with the downstream tasks.
But I'm getting an error (#1 below) when I try to build, because for some reason SSIS will not automatically add the new column to the Error Output, and it won't let me add a column to that output, even in the Advanced Editor. This is annoying. I'm probably going to need to delete and add this data source, which is going to screw up all my transformations.
Error Message #1
Error at Data Flow Task [tbCA Source ]: The output column "CaxSubTypeId" (1052) on the non-error output has no corresponding output column on the error output.
Error Message #2
TITLE: Microsoft Visual Studio
Error at Data Flow Task [tbCA Source ]: The component does not allow adding columns to this input or output.