Unable to Submit Additional Information For an Appeal Online

I have just spent a few weeks compiling additional information to submit online in relation to an appeal ,but when I click the submit tab it says - There are special character(s) in the text entered. Please remove these before continuing.
It doesn't tell me what they are?
I've used / - " ? ', . so have no idea which of those it might be , but when I look at the initial paperwork that I submitted for the appeal, all of those have appeared in it and there was not a problem submitting that.
So I am totally baffled as I've gone over it time and time again to make sure that I'm happy with it before hitting the submit your statement to the tribunal tab ,only to find that I can not submit it, so am hoping that somebody might be able to help?

Hi Gordon,
There was no file name I was typing it directly on the additional information page online and was responding to what the DWP have submitted in relation to my appeal. So it was just a case of type it all up and hit the submit tab and all of the different characters that I used are what I used within the appeal papers and there were no issues when I submitted that. So I have no idea what the issue is. I tried again today only to get the same thing happening so decided to ring up to see if they can enlighten me and was on hold for around 1 1/4 hours listening to droll music and repetitive messages telling you to go online. Eventually when somebody finally answered they said that nobody else has said that they’re having the same problem ,but it will be raised to the relevant people to look at and I was then advised to send the documentation by email and surprisingly the man said don't even consider posting it as it will take around 3 years for anyone to deal with it. Obviously I assume that he was exaggerating and I said that to be honest that's what I was going to do next and again he said don't bother I advise you to email it and even then it will be a couple of weeks before somebody deals with it. So it's not just the DWP who take forever to answer the phone and act on things HMCTS seem to take just as long, but at the end of the conversation he ended the call with Good luck with your appeal, it's not something I've ever heard from the DWP.
It's submitted so it's the waiting game now, but I've managed to find huge mistakes within what the DWP have submitted, so lets see what the DWP fire back at me or that's what I'm assuming will happen next unless it's just a case of wait for the date of the hearing?