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Periscope Reset

Is your periscope stuck looking at a weird angle? Can't see the horizon? 'Center Vertically' button broken doesn't help, and neither does restarting or docking and beginning a new patrol?

This might be able to rescue your save.

Load your save with this mod enabled.
Get into the bugged periscope view.
Open your chronometer to trigger the mod to attempt to fix the weird angle.
If it worked, save, quit the game, and disable the mod, you should no longer need it.

Opening the engine telegraph will log the periscope's state before and after attempting another fix, check output_log.txt for details of what it found.
Opening the rudder control will try to fix vertical alignment specifically.
Opening the compass will try to fix horizontal rotation specifically.
Opening the depth meter will try to override the vertical centering behavior if the 'center vertical' button is still behaving incorrectly.

I created this because my observation periscope was stuck looking skyward after I'd locked onto an aircraft using the map table controls, which persisted long after the aircraft was gone.

It worked for me. Your bug might be different.

Do not try to play the game with this mod loaded; I hooked into all the ui controls to get pieces to run on demand.

Just get your periscope reset and save to a fresh file.