Strange.

Weird that OT shows clipping yet signal is too quiet though. Phase issue maybe? (i.e. check input source is A B not A+B)

Also check out OT manual p44: The sampling input level (In the RECORD SETUP 2 menu) is separate from the DIR gain setting in the mixer page. Could this be the issue maybe? Are the monitor LEDS reflecting the recording gain settings and NOT the DIR setting? I think this is probably the root of your issue.

Hope this helps solve it.