Comment 2 for bug 1439160

The bug happens due to the special Lipshitz/Vanderkooy mix oft the two
Bessel EQs.
The filtered signal is added or subtracted from a delayed dry signal.

https://github.com/mixxxdj/mixxx/blob/master/src/effects/native/bessel8lvmixeqeffect.cpp

For performance reasons we stop processing the not required filters. This
should happens at unity and produces a bit-perfect sound. It turns out that
it also happens in you kill use case. After re-anabling a filter path, we
have to deal with silence until we are at the desired delay and the filter
is settled.
In the case you disable midi Kill, we have the transaction from the high
low bass stage to the low low pass stage.
Since the low low pass stage is not settled, some low samples are slipping
though.

The Linkwith-Riley type does not have the issue and works like you expect.

I will have a look how we can fix this issue.