When manipulating your Sends levels via the faders on your FaderPort 8 (as an MCU device) within Apple's Logic DAW you may notice some strange fader behavior.
We have found in our testing that MCU devices in general experience unexpected fader behavior when adjusting multiple Sends at once in Logic.
This is not a malfunction of your FaderPort8; instead this is an unfortunate side effect of MCU implementation within Logic.