Yes — as many as they like. Guests can go back and record again whenever they want.
How they do it
They return to the same page they recorded on the first time — the link in their invitation email gets them there — and submit another video. Nothing needs resetting on your end.
What you'll see
Each submission arrives as its own tile in your media grid. Keep them all, or remove the ones you don't want. See How Do I Delete/Restore Videos?
A word of warning
Several videos from one person adds up quickly, and a Tribute that runs long is a Tribute people stop watching. If someone has sent four, it's worth choosing the best one — or trimming each down to the part that matters.
Still stuck? Email support@tribute.co and we'll help you out.