Error: "The generated script can produce data loss. Number of warnings: 2. Do you want to proceed (4325637)

There are two Oracle physical models corresponding to two consecutive versions of the same database.

The purpose is to transfer all the indexes' definitions from the old model into the new one using the model merge functionality in Toad Data Modeler.

While the application starts processing, it displays the following message "The generated script can produce data loss. Number of warnings : 2. Do you want to proceed with script generation without check ?".

If the "yes" button is clicked, the merge stops and no index is transfered to the new model.
If the "no" button is clicked, an exclamation mark appears next to the  two tables.

After unchecking them to put them out of the scope of the merge, and after clicking the "Execute" button, it brings an "out of memory" error message.