That happens alot when people run out as the gates are closing. One time - I announced on the loudspeaker - if you are going to ride on this train - please take your seats NOW - the gates are closing. There were these people just standing there looking at with a dazed look on their faces. So after a couple seconds of them not doing anything I toggled the switch. Then the littlest of the group jumps out and the gate smashes into him and pins him to the queue rail. 95% of the time it is the guest's fault... But when it isn't the guests fault - which is RARE - we always try to open them again right away when we realize that there is someone stuck - but it takes a second or two for the system to respond...
I think all the rides need to start a policy like Holiday World uses - and Italian Job has - where the guests have to stand behind a yellow line on the ground - that is more than arms reach away from the queue gate. It would prevent over enthusiastic kids from jumping in front of moving machinery.