Nice work. I am thinking like Raj that issues are few on the circuit board, but maybe others have found faulty potentiometers.
Sensitivity is said to be 0.1 uV but no snr is reported, all of us tend to think our ubitx are as sensitive as most HF transceivers at least through 21 MHz, and likely within a couple dB above that. Fine for amateur radio. I am not familiar with v6, but many use headphones or an external active speaker.
The design uses no preamp but is nicely implemented, and it works. I am making stateside and Europe qsos this week on 40m ssb. I hope the op has some fun with it.