Hi @pmesquita,
As a first step, you can have a look at some of these posts here that report on a similar issue: Upgrade failed: DB: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry ‘index-6-blockTitle’ for key ‘plugin_settings_pkey’ - #4 by jorgelpolanco
However, others with more direct experience with issues like this one may wish to weigh in.
-Roger
PKP Team