CFD Simulation Issue

Hello,

My team and I encountered issue while we were computing CFD calculations. I attached pictures that illustrate the error.

This error occured after 4 rigorously identical steps (we haven't encountered this error during step 1, step 2 and step 3).
We then computed the step 3 again (it worked before) and the same error occured.
Finally, we created the same model from scratch on a new file and the error occured again.

Do someone know why this error occured ?

Benjamin