The accelerator is not smart enough and creates new columns when you drag and drop some columns from father tables to children tables:

As you could see in my table, there is already a column called ProductId and LocalUserId but the accelerator created new ones called ProductId2 and LocalUserId2.
When you create some relationships, OutSystems should ask you to confirm if you want to create a new column instead of by default creating a new column. This has created all these problems: