Log Analysis assistance please

Hi All

I have a new 3.8m VTOL from a Chinese vendor. It is a carnard design and has a 60cc IC engine as its pusher. Please message me if you want the sales page with more specifications.

We are operating it as default from the vendor but to be honest, its flying very poorly. We initially thought the CG was off as we had some terrible “dolphining” but this changed nothing when we added more weight to the nose. The drop in elevation is so sever that we have to manually land to avoid a ground strike on final approach.
Today we also had some issues with EKF3 lane changing errors that we think may be attributed to vibration. For a moment we had no communication with the aircraft and when it regained, we were heading in a completely different direction.

If anyone can help a poor guy out figure what is wrong with this aircraft, we will be eternally grateful. The log can be found here: WeTransfer - Send Large Files & Share Photos Online - Up to 2GB Free