Hello,
my FF400 is some years old, until now I used only front inputs (1-2 and 3-4) and output 1-2 or SPDIF.
All was fine but today I needed some other analog outputs and I found something weird, so I decided to do some direct input/output routing tests...

I launched a playback of 1kHz sinusoidal wave  @-10dB on all output channels (1-6)

Line in, Line out and Phones levels were set to +4dBu in Analog settings
gain 0=dB for in1-2 and in3-4 in Analog settings

I got the following MIXER readings (with default preset 1 loaded):

AN 1-6 -10.0dB
PH L-R -6.5dB

routing out1 to each input with single balanced cable
in1 -8.4dB
in2 -8.4dB
in3 -10.4dB
in4 -10.4dB
in5 -10.4dB
in6 -10.4dB
in7 -19.3dB
in8 -10.4dB

routing each output to in3 with single balanced cable
out1 -10.4dB
out2 -10.4dB
out3 -10.4dB
out4 -17.9dB
out5 -22.1dB
out6 missing signal

routing each output to in5 with single balanced cable
out1 -10.3dB
out2 -10.3dB
out3 -10.3dB
out4 -21.2dB
out5 -21.5dB
out6 missing signal

I tried again changing the Analog level settings:
Line in, Line out and Phones levels were set to -10dbV in Analog settings
gain 0=dB for in1-2 and in3-4 in Analog settings

and I got the following MIXER readings (with default preset 1 loaded):

AN 1-6 -10.0dB
PH L-R -6.5dB

routing out1 to each input with single balanced cable
in1 -17.2dB
in2 -17.2dB
in3 -19.2dB
in4 -19.2dB
in5 -10.3dB
in6 -10.3dB
in7 -19.2dB
in8 -10.3dB

routing each output to in3 with single balanced cable
out1 -19.2dB
out2 -19.2dB
out3 -19.2dB
out4 -26.9dB
out5 -31.0dB
out6 missing signal

routing each output to in5 with single balanced cable
out1 -10.3dB
out2 -10.3dB
out3 -10.3dB
out4 -21.2dB
out5 -21.5dB
out6 missing signal

In conclusion:
it seems that I have the analog output 4 and 5 channels always at a lowered/wrong level and output 6 channel completely broken.
In addition it seems that even the input7 channel is reading a lower signal level.

There is something I miss or I need an hardware repair?
I'm clearly out of warranty and I live in north Italy,
any help and/or suggestion is welcome and will be really appreciated.
Many thanks in advance for the attention,
ciao,

Andrea