Negative nut occurring intermittently
 

Hello
I am simulating an aircraft with the SA model.
Turbulent settings as per recommendations by Spalart and Rumsey. Coupled scheme with time factor 0.1 . All second order spatial discretization.

In my mesh, i know that i have a few (<300 cells in a total of 85million) highly skewed elements.
I also have very low orthogonality in some cells at different location.

In the first 5 or so iterations, i get a warning message that a negative nut was calculated. It then disappears till around iteration 700. After that it reappears intermittently with a warning in around 1 to 7 cells.

My x,y,z,energy, and nut residuals decrease steadily. My continuity however oscillates but also decreasing.

Is this occurrence at a higher number of iteration something to be worried about? Can the solution diverge at this stage?
If so, how do i correct it?