In contrast to my recent PS5 woes, how about an example of a 'user-unfriendly' error message that was actually shockingly helpful...
Background: A while ago, the gelfling started having issues with her Darkest Dungeon save games.
StorageManager::TransferFile in storage_manager.cpp line 936
couldn't write whole file?
ESC to skip
Googling that led to a whole slew of potential causes and weird fixes. Click the envelope, not the slot name, to load (even though both should do the same thing)... Maybe doing a shuffle and swtitcheroo between a clean savegame setup and a backup of the savegames? Or could it be some wonky interference from intel integrated graphics drivers? (No, really: that came up as a potential cause).
So today, since the issue had apparently become even worse, I actually Had A Look at it. Armed with backups, new folders, and even a dedicated graphics card (because why not), I sat and swore at it for a while because nothing really made any sense.
And then, whilst going to disable the steam cloud savegames, I Noticed A Thing. Steam said that there was something like 48MB of cloud storage in use... and only 2.8KB free space.
That's when it clicked. That error message, unfriendly, leading to so many dead-ends via google and prayer, was entirely accurate. Couldn't write whole file.
For, you see, the gelfling is a prodigious player of Darkest Dungeon and has amassed many hours of play in the 9 savegame slots the game allows. So many hours, in fact, that those savegames have grown swollen with the accumulated joys and miseries. Swollen to the point that apparently the steam cloud cannot take it any more...
Deleting a slot or two easily freed up enough space that the steam cloud savegames feature could start working properly again... and the error message is gone. And why did I think that would work? Because the dratted error message actually said what the dratted problem was.
TL;DR: if your Darkest Dungeon saves start not loading properly, giving the dreaded "StorageManager::TransferFile in storage_manager.cpp" error, and none of the 'standard'; fixes works... Maybe consider checking if the steam cloud has any space left for them (several megabytes free, at least) and also maybe a little self-check that you're not too addicted to DD.