RFC_ERROR_SYSTEM_FAILURE - A table or alias name in the FROM clause is not unique.

In a table extraction, several SAP tables are joined. 

However, the correct sequence flow of the table joins is not given and must be adjusted manually by the creator.

Make sure that the sequence flow is correctly defined sequentially in the Joins tab, see example:

Tab1 INNER JOIN Tab2

Tab2 INNER JOIN Tab3

Tab3 INNER JOIN Tab4

...