Internal spurs below 100kHz

I enjoy exploring the world below 200 kHz and my 6700 v1.0.0.99 works pretty good but only using the RXA or RXB inputs. When using the Ant1 or Ant 2 inputs internal spurious signals render most of the area below 100 kHz unusable except with preamp set at -10 db. When using the RX inputs the spectrum is relatively spur free with preamp settings at -10, 0, and 10 db. The 30 db preamp is unusable on any input in this frequency range, signals are 60 db down. Unfortunately with my antennas at these frequencies I need the low noise preamps engaged. I also noticed that the level calibration was very accurate when using the RX inputs on all preamp settings except 30 db however when using the Ant inputs, displayed levels from a calibrated signal generator were down 3 to 8 db depending on preamp selected. Here are screen captures of what I see with the different input and preamp settings. All inputs where terminated with 50 ohm loads at all times.