It seems that the problem was not the split recipe. It seems to be the lenght of the name of the datasets. It took both 3 datasets as the same because it only changed the last part of the name. Seems to be a problem with the names not with the recipe
Yes, you need to be careful with long table names on SQL connections. Many SQL databases enforce limits on the number of characters for table names, otherwise, they truncate it. It can result in hard to understand issues. If indeed your issue comes from this type of SQL limitations, I would suggest speaking to your DB administrator to increase the default setting on the number of characters for table names.