Hello Edvinas,
please have a look at the following post.
This connection caching is one of the reasons why we are rewriting the database extension. The new extension creates a new DB connection for each connector node an thus as no dependencies between workflows.
The new extension is already available as preview which you need to install via the KNIME Labs update site (see attached screenshot). Let us know what you think of the new framework.
Bye
Tobias