Also I deleted the database_table_734 that was making the vaccum process fail on my instance 
Glad to hear that you made it work! Do you have some examples on how to reproduce the problems with very long content in the long text field type, would love to investigate? There is an issue on the backlog to support a JSON field type (Support JSON (Objects) as a Field Type (#1240) · Issues · Baserow / baserow · GitLab), but the priority is low from our side.