Our freelancer suggested that we find a new developer due to time constraints. Is there a need to have them sign a lien release before canceling/ending an hourly or contract job?
I think (and forgive me if I have misunderstood the technical term) you are asking if you need the freelancer to release ownership of the work they have done so far to you.
Upwork's User Agreement (Section 8.6, Intellectual Property Rights) grants the client ownership of any material the freelancer produces which has been paid for. If the freelancer has already turned over all the work they have produced to date, and you have paid them for that work, then you own it.