Morgasmatron LP filters don't close all the way?

I picked up a Morgasmatron on the second hand market and was going through having a fiddle with all the modes, and I notice that the LP filters don’t quite close all the way. LP1 is a fairly small amount, but LP2 lets through a pretty significant amount of the signal. The cutoff knob is buried at the lowest amount, the In knob is around 10 o’clock, Q drive is down, Q is down, and I’m hearing a lot of the low end of the audio signal (square wave from Plaits). This is the same using either side, any filter blending mode, separate filter outputs or the Mix output.

Is this normal?