Have a look at this observation and compare with your configuration. (This station has a LNA in combination with the HackRF)
gain-mode: "Settings Field" in combination with other-settings: "AMP=14,LNA=40,VGA=26" opens the option to be more granular in your gain settings.
lo-offset: "200000" can be used to move the HackRF DC spike out of the reception area.
Jan | PE0SAT