I always enjoyed building mega huge transports on long tracks, but recently I've run into a freak problem that repeats itself far to often: Trains go to get serviced at a depot.
More specifically, trains that have traveled 1000+ tiles, that just passed a depot on the way into a station, as well as several depots on the way over to this station, slows down to a near-stop as in preparing to deliver its 450 tons of wood, suddenly on the last pixel before delivery decides to gun it out of the station to the depot on the other side for a service. This of course leading to the train embarking on a journey back to its original destination 1000+ tiles back again to turn around in order to go back for the delivery.
Yes yes, I've countered the problem by making tracks that route the train straight back into the station (which works slowly when 8 trains of length 24 does this simultaneously with 8 new incoming trains), and have increased the service intervals leading to these problems being resolved there and then.
My main issue with this is: This happens on scaringly many of the tracks I make. I somehow end up making tracks that allow trains perfectly timed past pre-station depots and into the station before suddenly needing a service. Trains needing a service has become my enemy, please help

Oh, and nearly all my stations look like this: (remake)