You are using a preconditioned conjugant gradient (PCG) solver for solving the equation system. The message indicates that the preconditioning part did not succeed. In general this points out that there is a stability problem in the model. So even if the model converges after that, I would try to identify the reason for the instable preconditioning. If the message is shown in only one time step of a transient solution, however, you might also just accept that. It is hard to say in a general case what the effects on the results are as the message only indicates the instability of a mathematical operation.
