Queries time out to Postgres

I have copied the metabase jar onto a ubuntu 18.04 box.
i started it and went through the setup (as in, i connected a db).
The UI read my tables from db and offered me to create dashboards. However, no data out of the tables was ever read. If i try to submit queries, they fail (as in, time out).

This is Postgresql 9.6.3 (RDS in AWS).

The user creds i used work when used in pgadmin, and metabase was able to read table names, so something must be working?

This seems to be caused by the automated dashboard trying to auto-analyse one of our tables - if that starts, the whole metabase hangs and no queries are processed. if we skip that and just run questions, the system works.