Thanks Mihalcea Vlad I verified the issue and created 2 PR that should fix it.
in order to avoid gaps in the id generation i also changed
// Some comments here else if ( ! generationState.hiValue.gt( generationState.value ) ) { ... }
to
// Some comments here public String getFoo() else if ( generationState.value.gt( generationState.hiValue ) ) { ... }
PR for 4.3 branch https://github.com/hibernate/hibernate-orm/pull/971 PR for master branch https://github.com/hibernate/hibernate-orm/pull/972