OraclePlatform is using the ALL_* tables to fetch schema information but is only supplying the table name in the where condition. This causes problems when you have multiple schemas with tables that have the same name. Their columns/FK get mixed up.
My colleague and I have traced the problem down to the OraclePlatform class and replaced the ALL_* tables with USER_*. The fix for that is on github https://github.com/FranPregernik/dbal/commit/c70bc462b49a168105304cdff0086dcd15cc347d.
As mentioned in the comment message the other fix would be to fetch the schema name (user) of the table and add it to the where part of the queries. Something like this:
t.owner = user
A pull request has been made on github for this.