Most likely the problem is the BFO adjustment. We would need more information on which model and what equipment you would have for testing.
I personally have found a free Audio Spectrum Analyzer (google one on the net) was the most helpful. You can plug in a usb mic, have it close to the speaker of the uBitx, tune to a clear frequency, and adjust the BFO for the noise plateau to be centered between 500 and 3,000 hz. The BFO has the most impact on the receive sensitivity.
There are other methods on groups.io. You can search for them with BFO Setting or something simalar, just remember that the v3 and v4 are at a different frequency than the v5.
Hope that helps,