Without getting too technical...it could have been a number of things that caused this... The inital issue sounds to me like it might have been a safety 3. Basically if the CM in the station hits a console "station stop" (for whatever reason, usually because someone is not where they are supposed to be) and a train on the ride itself gets caught on safety break 3, along the river just before coming around the corner to get back into the station, they can not reset the ride. It has to be evacuated and Maintenance has to come out and winch the train that is on that particular safety break (this happened A LOT before the load gates where installed, it still happens but far less than before). As for your other ride, sounds like they had the max number of trains out. If they are running the max number of trains and the trains in the station get held up (slow loading, a dispatch issue, whatever) then the trains that are out on the ride will accomodate for that, the system will pick up the fact that there is a back up and slow (or stop) the trains that are out so as to keep the spacing at a safe distance...