Question about Kandao Meeting Pro

We tested the device intensively for 3 hours on all possible types and platforms. However, the online participants complained of such poor sound quality that a business conference would not have been feasible with it. The device was immediately returned under warranty with the note "micro defective". We received our money back without comment. Before we order again: Did we receive a defective device or is this a fundamental weakness of the Kandao Meeting Pro - what are your experiences?