DC offset voltage on DSO Quad inputs(!) and output

Hi all,
I’m seeing about a 1V DC voltage on my DSO Quad’s analog inputs and on the signal generator outputs.

(The DC offset is not a measurement error, i.e. it’s not merely the AC signal from the signal generator being rectified/filtered by my multimeter.)

What could be causing this? (I have not calibrated it, I don’t have a proper bench power supply.)

Never mind, it looks like the DC was coming from the device under test in a very weird way. Oops.