If there is a legitimate explanation as to why 'technical issues' have made it impossible to file a witness statement for a hearing they have been aware of since 10th December until 3 hours before the hearing, then it is an explanation beyond my comprehension. They could have got around any such issue (if one existed) by attending the hearing...
I think your primary point on the WS is as I noted above, that serving one so late is on its own unreasonable, then if you need it, you can draw attention to the fact you disagree with some of its contents, as Intercity rightly notes.
Good luck - have all these arguments ready to go - depending on the judge, you might not have to say much (particularly if it's the same one that struck out their claim in the first place). Let us know how you get on.
