So far.... had a persicope that would not zoom in. Which I figured out in rough seas while trying to spot a group 4-6km away.
I think theres a water seal problem/sabotage. I've randomly gotten slow flooding and negligible damage( like -0.7% integrity total) while doing test dives at 50-100m in a IXB
I was outside minefields/nets and the flooding got worse as I dived like I had taken previous hull damage. Now I make it a habit to test dive in the deep Wilhelmshaven port before leaving the dock area. I didn't dare take it past 100m.
The worst was an engine malfunction. My max speed was 14kts in smooth waters while at flank speed. I kept thinking my battery was drained. While testing out the pre-set speeds they all made me go 3knts slower. While underwater I only had a 3knt maximum. My battery also went really quick.... Not sure if this was electrical/diesel or the whole system.
Cool topic, love the malfunctions/sabatoges. I try to ketch them before i leave port but a new one always makes the checklist or can't be tested before its a real problem out at sea.
Test procedure for me: Check to see if conning binocs work. Then periscope raise/lower and zoom.
Check speed on surface and then dive to 30-50m. Anything else is un-detectable to me.