We are using DT Register 2.7.3c. This is the first time I've used the updated version as we were previously using a 2.6 version but wanted to wait until the end of the school year to set up the new one (we're a volunteer organization).
I have conditional fields set up for an event that have a selection limit of 1. Meaning only one person can register for that spot. The field type is radio button.
When I register for that spot, the field is still there upon return to the event registration. The radio button is no longer clickable but the option is still in the list.
I think we had similar proble in version 2.7.6. Fortunately, after upgrading to version 2.7.7a this problem disapeared. Hope this will also work for you.