Mouse...
Ok, to begin with... good call... on NOT following the normal 'default' install trainwreck location, to do that step.
Has been some time, since I've... rolled out with SH4 stock.
As far as patching to update or keep it up to date, is a moot point there... owing to the fact... that is to take & bring the original release of SH4, which was... v1.3/1.4 named Silent Hunter IV: Wolves of the Pacific, up to Silent Hunter IV: Wolves of the Pacific: Uboat Missions v1.5, or as Ubi has it tagged, "Gold Edition".
So... no patching or updating required... unless you have 1 of the early releases of it, to begin with. In that instance, if able to do so... then would be easier, to just pay for & grab SH4 v1.5 & replace the older copy, out right.
Just, My own personal observation/opinion there...
In your case, NOT needed... as you have v1.5 "Gold", from Ubi.
Now...
as to your, finding your sub, all of a sudden going from A J squared away, in perfect condition to... crew screaming in fear & for a meedddiiiicccc.!, all those nasty damage reports flooding in, just as bad as holes in your boat...
could be a couple of things... namely, it is possibly conceivable, you hit a mine... or, could have had a IJN aircraft drop down on you like a Falcon... & delivered a bomb or a couple of depth charges on to your sub... gonna say, I seriously doubt it was a ship... though, if you were near any small spit of land isles.... it is possible to have taken pot shot hits from a land-based gun emplacement... with Superman, manning the triggers & controls to it.
That, above... coupled with your stating, findings of... changing views, of still remaining in high TC.... could well account for it.
Can't recall of any times I've experienced a remaining in high TC mode, when going from say... the control room, to... the bridge... but... it isn't outside of the realm of possibility, either.
If, I recall rightly... with Ubi (formerly Uplay) Connect... in the library section, it is doable... to have it to check the 'integrity' of the game install... & might be advisable... to run a verify game files run on the install... just to make sure everything, got installed... rightly, as it should.
Is rare, but... screw ups, can occur when downloading files & such... & that of course, includes games, as well.
I'd think, that running that integrity scan, should NOT impact the 'game saves folder'... but... as a precaution... might consider, wiping it out & starting fresh... just prior to running SH4 again, after doing that integrity test...
just to be safe.
Hope this helps...
Fair winds, smooth seas, &.... Good huntin', skipper.
M. M.