I am working with SSIS in Visual Studio 2019, and I am trying to do something fairly simple. In the data flow I load data from two flat files (basically, half the data set in each file), union them together, then after doing a few simple derivations and a lookup, I save the data to the database. The Data Flow looks like this:

Now, when I had this with a single input file, it worked perfectly. This error only cropped up when I split the data between two data files and tried to union them together.

Double-clicking on the union I see that all input from the second file is set to ignore. When I try to set the input 2 to map CityName to CityName, I get the following error.

I have no idea what this error means, and I haven’t found anything on point in my searches. Does anyone have any insight to offer?