Okay, here are the instructions:
1. Grab
this file.
2. Rename the extension from .whl to .zip and unpack it.
3. Navigate to PyQt5/Qt/bin.
4. All potential dlls we might need are here.
These dlls should be dropped to the client installation directory (wherever other dlls are, I believe it's the root folder). You can try dropping them all in first to see if the issue goes away, if you don't mind reinstalling the client afterwards to clean up. Other than that, it's just a matter of dropping libraries until things work.
If it still doesn't work, then try the same thing with libraries from
here.