Multiple custom columns created when using Spreadsheet and loading with JDBC?

Hi,

I noticed that when I use a spreadsheet with Multirow Store Binder and JDBC Load Binder there are multiple columns created in the database. this happens when I use "Select * from app_fd_tablename"

In the picture, there are 6 X "c_" because I saved the form 6 times. I think the behavior does not happen when i use a more restrictive select clause like "Select c_Status from app_fd_tablename".

When the columns are created, the app will take a longer time to save because new fields are created in the DB.

Please confirm if this is a bug. Thanks.