I think it might be your word processor will have a very irritating thing with the way it views certain letters and so you might not pick up on an error, I had that exact percentage until I realised my problem for 4A.
This isn’t major but when I put in http://www.cipher on my iPad (iPad Air running iOS 11.1) it comes up with National Cipher Challenge 2016 under the link in the suggested when it should be 2017.
If you open a new tab to submit an answer, you can use the original tab to submit an answer again as it doesn’t have the “your answer was 100% correct, you don’t need to submit again”. The duplicate answers also appear on your answers tab.
the message to display next boundary ( at the moment it is 14:11 on Thursday 16th) shows incorrectly, currently being “Countdown to deadline for challenge 5” when it should be “Countdown to challenge 6”