I’ve 2 terminal: 1 for small planes working fine and 2 for medium aircraft (at the moment there are only the runway, the stands and public transport stops).
Some of my workers (especially administarator and contractors) arrive on the terminal 2 and remain stuck (there is no connection between the terminals) although there are no staff rooms or franchise in this terminal.
There should always be a connection between terminals, as personnel can be assigned or re-assigned to another terminal then where they arrive or work. So please start with building a connection between the terminals and report back if they are still stuck. A save and reload could also work after you have created the connection and they do not move yet.