Just came to report the same thing. Some extra information:
** See Addendums -- May or may not be accurate, further testing needed**When trains start rolling forward (back of train UP a slope) or backward (back of train DOWN a slope) after arriving at a station and begin docking they automatically move to the next station but get stuck in 'Docking Mode'
This bug appears to (also?) occur on totally flat tracks with *Multiple* locomotives.
Test 1: Loco<-->Car - flat track built on linked foundations - No issues, Train stops for the full animation at each station.
Test 2: Loco<-->Car<-->Loco Train enters loading station, stops, starts 'Docking' Starts to pull out of the station immediately.
This bug severely limits the maximum number of freight cars per train if there are any inclines in the track. Considering the likelihood of a totally flat track or only small inclines, the maximum number of cars is realistically limited to 3-4 before you need a new station and train as 1 Locomotive isn't capable of pulling 5 loaded cars up anything more than a short, gentle slope.
Note: Further testing required, If this isn't patched by the time I can test more tomorrow I will do further testing on 1 Locomotive 3 car setup on un-even ground as, if I recall correctly, the first tests were done with a 3 Locomotive <--> 11 car and 2 Locomotive <--> 5 car train
'Docking mode' appears to alter maximum throttle instead of braking(?) The alteration is significant enough that the train can't climb a steep incline (more than a 176m x 88m - Horizontal x Vertical or in 8*4 foundations: 2 across, 1 up/down) but not has no impact on making the train remain stationary at the last station through the entire docking process.
Trains will leave a station but remain stuck in 'Docking Mode' until a player manually completes a Docking cycle at a station. Upon the AI's next visit to that/a station, the issue reoccurs.
When stuck in docking mode, If the AI makes it to a station that it does not roll at, it will not attempt to dock at said station. Instead, it will stop completely before continuing on to the next station. Addendum: If you remove and then add a Locomotive to a train stuck in Docking Mode, OR attempt to complete a docking while manually controlling a locomotive OTHER than the 'Primary' Locomotive on the train (the one that stopped in the station) this will cause a full CTD and crash report. Easiest replication was to add a new Locomotive in front of the existing one and attempt to dock, CTD ensues.
While stuck in 'Docking Mode' the train appears to still be able to load/offload goods the animation plays, however as noted above, the train does not wait for the animation to complete before leaving (can say loading 100% works, empty freight cars and then boom, magically the goods appear in the wagons 1km down the line and the wagon goes from being visibly 'Empty' to 'Container')