I remember this problem from an earlier post when all sorts was suggested and tried.
I don't wish to be gloomy, but could it be the scanner itself which somewhere along the line has stopped either collecting data or is not making sense to the driver?........
I say this because what was working well seems to have ceased to function without anything else being changed.
If something has failed and the numbers don't add up to the Twain driver, it could be the reason for your error messages, and sadly time to think of a new scanner.
Stating the obvious, there is no chance of trying it all on a trusting friend's computer?