Not sure if duplicate words are valid, but I guess the grid works ok.

To answer that, as its a FAQ on here- I tried the correct combination for that group and it didn't work. I tested it with the duplicate word and it worked, so yes it does affect the grid- finding that one word works in two groups is an ideal opportunity to add a red herring, this may be preferable to you than using it twice? :)

Very good! Spotted three groups early and then got puddled. Good work!

Good grid, though I'm not keen on duplicate words.