Sinking for no reason.

[Vonotto]

I loaded up the new NYGM mod and am on patrol....have left port, no damage ect new crew..... aircraft is spoted and I dive to periscope depth.....a few minutes later im at 2 knots and NOT silent running, when I begin to sink I order a return to periscope depth but I continue to sink....I order flank speed and a return to periscope depth but continue to sink.... i blow ballast and order periscope depth which works for a few minutes until I again begin to sink.


ANy ideas what give with this.....it make NYGM completely unplayable for me because I can neve stay at periscope depth for long, even while moving.