Submarines don't seem to hold their depth when they're on a different side than you. Test scenario is attached, it's just two sides, Red and Blue, with a single Blue sub. Set the depth of the Blue sub to something other than Just Over The Layer, and it'll go to that depth. Then switch to Red side and watch in God mode as the sub goes to just over the layer. Then switch back to Blue side and the sub goes back to whatever depth it's set to.
This seems to happen with both a manual depth setting and with the Depth Presets. The sub has no mission set, just a waypoint and a manual speed of 10 kts, and the doctrines and WRA are all at their defaults. However if you make an ASW mission and assign the sub to the mission, the same issue occurs where the sub only respects the assigned depth if you're on the same side; as soon as you switch sides it goes to "ASW behavior" where it alternates above and below the layer.
This problem has reappeared with version 1.15.1 (build1009.27.3)
In the Tuturial 2.1 Submarine, the Han does not maintain its manually assigned depth of -984ft and rises to -348ft.
This makes it impossible to detect if you follow the instructions of the tutorial.
To all English teachers of the forum, sorry if English is not my mother language.