Once I enter my PIN and start my voting process, do I have to vote for all the races on the ballot in one session?

Yes. You must complete the entire voting process in one session. When a voter is timed out by default, or when the session is interrupted or terminated (intentionally or not) before the final ballot is cast, no information is stored, and no votes are counted. This practice always guarantees the voter’s privacy. If your session is interrupted, you will have to start the voting process from the beginning.