The default HPF in mixer mode, where the resonance parameter can not be adjusted is set to a very high resonance level. Using it always creates the typical sound artifact and for me it is very unwelcome unless I specifically want to hear it. It also seriously pushes the gain level up. If you use it when you're already near the clipping point, it will definitely push over, especially in the low range.

I am aware it can not be adjusted from software in this mode, but maybe it could remember a setting from the last usage or just not have resonance by default. As it is, for me it's more of a bug than a feature, but of course the general consensus may be different.