HI CaptBones,
it's deliberately intended that the depth gauge shows 0 meters, otherwise too many players will have a problem with it. It symbolizes surfaced. It's not a bug, it's a decision made by the devs.
Why don't you give an order not to use the obs-peri? You can generally forbid it in crew-management or directly at the periscope with RMC if it is a short-term order.
No, the periscopes are retracted at a slightly deeper depth. But you have probably already noticed this.
Cheers Ruby
