Possible Glitch?

[Ski206]

I recently downloaded SH4 to a Windows 7 Pro laptop and have been playing for a few weeks. I'm in career mode early war with a Tambor class boat. Several times when submerged with enemies nearby but without any action from them I've all of a sudden been overwhelmed by damage reports and the sub sinks.

A couple of examples. Cruising on the surface and radar detects a plane inbound so I dive to 100' never having seen the plane. All of a sudden I'm taking damage (no explosion sounds) and I'm dead.

Or tonight I maneuver dead center into a multi ship convoy pop off all 10 tubes sinking 3 ships with 2 damaged and then dive deep (@300') beneath a thermal layer to make good my escape. My escape takes me right under one of the merchies and while destroyers are milling about camera view shows none close and none dropping charges. Nor are the sounds of explosions heard. And yet in roll all the taking damage reports all of a sudden and down she goes.

Is this a glitch or am I missing something?