Oh no! I am still trying to figure out your issue. I have replicated circumstances based on what you told me and not had the same results,
unless I am running above 100 RPM and not on silent running or I am on surface at too close visual range and dive. They spot me but even if do not spot me such as in low visibility, they heard me dive because I am too close when submerged (boats are noisy when dive and surface)
Exception being when off Okinawa a patrol plane, not seen when periscope was up, only when went to external view to check behavior or enemy vessel did I hear, then spot the PETE above. PETE was unarmed, but the DD turned toward me at high speed, came in pinging, dropping charges. Before PETE was above, DD was sailing along st 4500 yards, unaware of my presence.
Would mind posting your mod list?