Sound Issues with percussion and quieter tones

[MtnRhythms]

First of all, I already have Original Sound turned on and echo cancelled etc as recommended to the pianist. I have upgraded my Mac to latest OS. I have switched computers. Ipods and every cable connected to my Mackie FX6 Mixer. I have even replaced the Mixer but with the same model. Nothing has improved this situation. I have been on the phone and email for hours with Mackie. No one knows what the darn problem is but the sound is unacceptable for my movement and drumming events.

I am having problems with certain songs that have a very delayed start and/or comes in and out. Percussion pieces do not come through at all. Choppy or crackly sound often.

I have asked Zoom Support for a list of supported or recommended sound mixers but haven't gotten an answer.

Any ideas???? Is anyone using a mixer without these issues? Thank you!