That's a good point, I hadn't considered that aspect of the dummy station thing. I found that if I deleted two of my three cargo stations, that had enough of an effect on the incoming trains to make them use only one track. Of course, now I have a backlog of incoming trains (not to mention terrible road traffic) because one train station can't handle the cargo traffic of the entire city, but that's a new problem. The upshot, then appears to be that it's an unavoidable design flaw in the game. :-(
It's not a design flaw. It's a game mechanic.
You can clearly see the insane amount of traffic (passengers) waiting for trains to spawn, as you have way too many train stations in your city, as previously pointed out. it doesn't matter that they cross over, i.e. the train tracks would still be full from spawning new trains constantly.
I'm sure if you looked at your trains, you'd see they are practically empty. This is a sign of too many stations on a track. Each track has a very limited capacity for trains. Just like streets. So, the game starts spawning trains that are not full at first, to give you warning of impending doom. Just like the single lane backups on your streets for vehicles.
But traffic jams happen prematurely as a gaming mechanic, as the game has a very limited number of active agents (moving vehicles) that it can spawn at one time. So it causes weird behavior prematurely, so your city doesn't collapse suddenly without warning.
You just need to look for the warning assigns, and fix them ASAP. They basically all come from zoning imbalance. Things should be built with purpose or they become imbalanced and eventually send your city into ruin, from imbalance send cims to places they don't want to go.
If you post a saved game, when can likely offer some specific advice that may not seem obvious as first sight, from the odd behaviors of the gaming ends of the rules.