I have a valid looking solution for Saturday 29 Sep.

There is a single loop, and all clue cells have been checked many times.
Is it possible there are multiple solutions? I can see 30 people have solved ok...

Does the checker compare the submitted puzzle against the expected solution, or does it check the validity of the submitted solution against itself?

Thanks

As far as I know, the puzzles here are supposed to have guaranteed unique solutions, and I personally don't recall any such problems with that puzzle. Can you take a screenshot of your solution and upload it in a new thread marked with the puzzle date, so it won't spoil anyone who hasn't solved it yet?

I can't submit about a daily puzzle until I've solved it.

I have your email though...

I've spotted my error finally! <monkey_face_slap>

This gave me an idea, so I've made a slight change.

Now when you click "Done It!" and the puzzle isn't complete, it'll optionally give you a hint (after a 10 second delay) as to what is wrong - for example "a 2 has only 1 line".

It might just help with spotting your error.

I like the idea of that!

On the variations, it's sometimes REALLY hard to see where the error is...

I was thinking about the 'fix' option. I've done other online puzzles (eg,at janko.at) and they have a back/undo button, so you can go back as far as you need. Is that possible?