I have found that in my park this message occurs when guests try to get home and want to use the transport ride to do so. Unfortunately, they want to go home together with hundreds of peeps at the same time so the queues for the transport ride get full. Normal guests that are in the park that encounter this full queue will just turn around and choose another destination, but the peeps heading for "home" apparently cannot do that and keep standing there in front of the queue confused. Even when the queue empties, they sometimes stay in this confused state.
I assume this is a bug. Why don't they opt for a walk home or walk to the next station instead of getting frozen.