This may be a question that is more generic to Panasonic camcorders, but I'm not used to this type of behavior with Sony and JVC camcorders we've used. Basically, with mics connected to the XLR inputs, I would assume that manual is manual and that auto is using some auto setting with AGC. That's not happening.
I know, I know, never use auto AGC. Here's my only application-location run/gun filming. I currently have the 160 set so that I plug my shotgun into channel 2 and set the switch so that channel 2 feeds both channels. Channel 1 is set to manual and 2 is set to auto. I found an internal setting under "Recording setup" where I changed Channel 2 to, "Audio Limiter CH2" to "ON". Doesn't seem to make much difference and I still get the meter banging in the red on auto with this setting. I know it has to be user error. What am I missing?