The problem is very likely to come from your database.
Assuming you are using Postgres, there is a default length for labels.
It works in such a way that you can write with a long string for this label, but Postgres by default will truncate it as per the documentation
DSS did write his schema with the label you provided when creating the output dataset, while Postgres truncated it, that is why after the recipe completes and DSS tries to synchronize his schema (with the accurate label) with the Postgres schema (with the truncated label), it gives an error.
As per Postgres documentation you can raise this limit in the Postgres config
The system uses no more than NAMEDATALEN-1 bytes of an identifier; longer names can be written in commands, but they will be truncated. By default, NAMEDATALEN is 64 so the maximum identifier length is 63 bytes. If this limit is problematic, it can be raised by changing the NAMEDATALEN constant in src/include/pg_config_manual.h.
Cheers from DKU