sounds like you messed up the patch process, I'll give you a full guide on how to install it
1.Download
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you can also find the same link on official wiki page
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2.I'm not sure if this is necessary but you also may need to download the latest translation files
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3.Extract the One-Click_Patcher executable into your game files and execute, it may fail the first time around but thats ok, we just want it to create the folder that comes with One-Click_Patcher execution.
3.5(Optional) If you download the translation files you need to use the 'Start Patcher' windows batch file inside the One-Click_Patcher folder to apply the translations. Since you got an error that probably includes mistranslated objects I highly recommend doing this as it may fix the game if you are unable to open it or access the LoC.
4.Download the LOC part 3 demo mod and extract it indie the One-Click_Patcher file that the One-Click_Patcher executable creates.
5. You should see a windows patch file named Demo LoC. Run it. Wait for it finish. Enjoy
Let me know if that doesn't work!