Hi,
First, sorry for your troubles with the uke, we are looking into them, we saw your email and we are checking the technical details with the team.
Feedback is usually a "part" of trans acoustic pickup system, so its always present to some extent. Each piece of wood and instrument resonates and sound s bit different, so its best to use and set the control to fit each instrument. Usually with effects and musical instruments, setting them to 100% is not a good idea, as the sound can be washed out, too wet and cause feedback.This goes to effects pedals, processors, amps etc. Similar to putting your phone volume, tv volume or amp volume to 100% results in clipping etc. We suggest to adjust the controls to fit the sound of each instrument.
We will try go get feedback from the AUS distribution, if there is something wrong with the item.
Sorry again, that you you were not satisfied with the uke.
thanks !