Despite it being a very busy evening on the GEML, the real life timetable for your service does contain a fair amount of slack to account for this which can see extended dwell times at stations. This includes a planned 4-5 minute wait at Witham to allow an express service to pass as well as a wait for an available platform at Colchester.
This service is DOO (Driver only operated) so remember to also close doors at all stations once passengers have boarded. Please also remember that the maximum allowed speed of your Class 321 EMU is 100mph. When approaching the buffers at Colchester Town don't pull up too close as this may result in the doors not opening correctly. Try and stop before the two TPWS grids with the rear of the train near the end of the platform.
I have seen instances on different forums where this route has crashed for some people in the Stratford area. When 32-bit was the only option, I used to turn water quality down and this eliminated crashes or me. Since the addition of 64-bit, I haven't seen any crashes at all but that workaround could be an option for those that experience it. As this particular scenario takes place during a busy evening on the GEML, the sheer amount of AI trains may cause framerates to suffer and may even have the potential to cause a crash on lower end systems.