When you duplicate a Matrix field in EE1 with MSM, Matrix isn’t given a chance to duplicate its columns as well, so the result is two Matrix fields sharing the same columns. This becomes an issue when you edit or delete a column in one site, because the change affects both Matrix fields.
This extension resolves that problem by auditing each of your Matrix fields, ensuring that all column associations are unique, duplicating columns and migrating data as needed.
To install Matrix Tidy Cols, upload ext.matrix_tidy_cols.php to your system/extensions/ folder.
Whenever you duplicate a site with MSM, make sure you go to Admin > Utilities > Extensions Manager, and click the “Enable” button beside Matrix Tidy Cols. The script will run, and you will be given a log of what happened. After returning to the Extensions Manager page, the Matrix Tidy Cols extension will still be disabled, because it doesn’t actually install any extension hooks. Don’t worry about it.