Locking the players in the seat deals with player movements, and those players definitely are able to be moved. When tables are collapsed, every effort will be made to keep them in their seats, but if that table is collapsed, they will move to a new seat, and I believe be locked in to the new seat. There are other threads that talk about a round-about way to do it, but there is not currently a fool proof way to do it, especially if you're looking to track chip counts with it. To prevent player movement, you can un-check the "automatically suggest player movement" box, and then you would manually move players.
What's been suggested (from what I recall): Buy in players for day 1A, play out til day ends, move to seperate table, and lock in their seats. Reset, and repeat for each day. Another suggestion: create a league for day 1a. everyone that plays 1a is a part of it. Once busted, remove from the league.