We have a sequence defined with the format:

@SequenceGenerator( schema="packing", name="packing_seq", sequenceName="packing_seq", allocationSize = 1)

The following SQL gets generated:

Hibernate: select packing_seq.nextval from dual

instead of the required

select packing.packing_seq.nextval from dual

which ends up generating a:
org.hibernate.engine.jdbc.spi.SqlExceptionHelper - SQL Error: 2289, SQLState: 42000
org.hibernate.engine.jdbc.spi.SqlExceptionHelper - ORA-02289: sequence does not exist

Our workaround for now is to define the sequence generator as:

@SequenceGenerator(name="packing_seq", sequenceName="packing.packing_seq", allocationSize = 1)

The same issue has been reported in the past and closed, mentioning that the above wasn't reproduced on version 5.0.6:
https://hibernate.atlassian.net/browse/HHH-7232