If you're in dual mode, I think you can only set the line level input number in the "dual" screen, where you select line, mic, dual, etc. You can only adjust the input level with the rocker control on the side of the unit. It shouldn't impact the line level when you adjust the mic level. I am not sure why that is happening with yours. I just checked mine, set the line level at 95, then went back out and adjusted the mic level up and down, and it didn't impact the line level when I went back in. Maybe try a default reset, or flash with latest firmware??