Problem with Import Table Data in 11.5

I believe I've found a bug with Import Table Data in the new version 11.5.
This is the scenario: Loading a tab-delimited text file into a table with
four columns.  For the majority of rows, the fourth column is null. In my
original input file, a value doesn't appear in the fourth position until
row 107. When I get to the file preview, the fourth column isn't displayed
at all and I have no way to add it.

Failing that, I edited the input file and moved one of the rows with data
in the fourth position to the beginning of the file, thinking that would
goose the import into loading the fourth column. Now when I get to the file
preview, the fourth column is indeed listed, but the value that is in the
first row is propagated to all the rows instead of being null.

I've attached two screen shots. 11_0 shows the data as it should look. This
is from version 11.0, where it works fine. The 11_5 file is the way it
loads in 11.5.

Excel input works fine, so I have this as a workaround.

(See attached file: 11_0.png)(See attached file: 11_5.png)