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The current save/load functionality doesn't save the transcript (your commands and the game's responses). So when you load a saved game after taking a longer break, there is no way to review what exactly you did previously and which puzzles you already solved. You can only reconstruct that information by what items you currently have and what locations you have access to. If the game is in an unsolvable state, you can't "debug" your command history.
[I faced this problem a few months ago with Guild where I couldn't get into the Bank even though it looked like all puzzles had been solved. I shared savegames with Stephan who deduced with some detective work that I had lost the silver plectrum, but could not determine how this had happened.]
A save/load that also saves and restores the transcript would solve these difficulties.