Elevated Events & Gift Aid

We are using an Elevated Event for our big gala in January and, for the first time, have a ticket cost which includes a donation, which could be eligible for Gift Aid. The event is set up with deductible and non-deductible amounts, and the relevant fund has the right GA type. Because we are not issuing tickets ahead of time, the payments are going through as a contribution with a designation of being a ticket (we have other designations for donations, sponsorships etc). However, Tessitura is not recognising the non-deductible amount and calculating GA on the full ticket cost rather than just the donation. How can we get Tess to recognise the split and create GA on just the donation?