If starting air line safety bursting disc damage due to excessive pressure during maneuvering how can we continue without stopping engine?

It depends on what risks are you ready to assume and what kind of maneuvering you are performing. You know that an explosion in the starting air line is one of the worst nightmares in E/R. I assumed myself the risk to allow several kicks on an arrival maneuvering in a terminal that banned one sistership of mine because of the same reason. Practically. I knew that the starting valve is ok but the landing face of the starting valve inside the cyl head pocket is not gas tight and I kept the starting air manifold drain open and I HAVE ROTATED THE CAP OF THE VENT for that particular unit such a way to obstruct the vent holes (I loosed the butterfly bolt of the cap, then I turned the cap and re-secured with the butterfly bolt). The engine was a MAN B&W 6S70MC.