Which sentence from the title sounds more natural when asking for clarification about something which has already been discussed? Is one tense preferable overall? Take the following examples:
Where is it they said they live/lived again?
Whose mittens are/were these again?
How many cookies does/did she want again?
When are/were we leaving tomorrow again?
Personally, I'm much more partial to the past tense. Since the issue at hand has already been established beforehand, you're simply restating it in question form as something new with "again".