Why does my sub keep sinking? (using the Grey Wolves mod)

[Snaggly Pete]

Several times while playing I've noticed that the depth of my sub keeps falling and I can't figure out why or seem to stop it. For instance, I'll set the depth to 60, but the sub will pass 60, 70, 80, 200, etc. (At some point, I'm sure the hull implodes, but I usually reload the game before that happens) I'm pretty sure it has always happened after the sub has sustained some damage, but from what I can tell the damage should not have been that severe to cause this.

Anyone have any idea what is going on and how to stop it? By the way, I'm using v. 1.03 of the Grey Wolves mod.

Thanks for any help provided.