After I knit the surface some blue sketch lines presist

If your gaps are larger than your knitting tolerance, then they will not automatically be closed. Pull the sliders to the minimum and maximum respectively to ensure that all gaps are shown, and either increase your tolerance or manually select the larger gaps that you would like to knit.

P.S. This screenshot is not taken from the same model as you - I just spent a long time trying to force some significant gaps - not easy to have an error when you're trying to get one!!