Duplicate Records on First run with Incremental Model on BigQuery

Hello dbt folks!

On one of the use case we have on our organisation, we have incremental tables which basically hold the append-only records of incoming events and current tables which stores the latest snapshots of incremental records with a unique key.

Above use-case looked us like an exact match to implement incremental model for good.

Documentation states that;

the first time a model is run, the table is built by transforming all rows of source data.

Because we have more than one record with the same unique key on our append-only incremental tables, the first incremental run generates more than one record with same unique key on current tables. Hence, consecutive batch following error;

UPDATE/MERGE must match at most one source row for each target row

Could anyone please let me know how this issue can be addressed with a solution or am I missing something?

Thanks in advance,
Soner