Less than 24 hours after I get my computer repaired and TS2018 up and running and I already have an odd story to share. This isn't a "problem" per se, but something just odd, along the lines of my other odd story back in TS2017 "A Legit Runaway" where I somehow enacted a runaway train situation while testing my Dash 9 mod on a coal train on Horseshoe Curve (if you haven't read that, go ahead back to TS2017 in Railworks Hall and check it out).
This one occurred just this morning while running a train on Sherman Hill. Last night after firing up TS2018 I decided to start work on a Christmas-themed scenario for the Workshop on Sherman Hill which I'm calling "Armor Yellow Santa", where you take a high-priority 111-car stack train with 4 ES44ACs from Laramie to Cheyenne (with rolling start) in the middle of a snow storm during the night a few days before Christmas via Main Track 3 through Red Buttes, Hermosa, Buford, Granite, and on to the depot at Cheyenne for a crew change. High-priority traffic is typically scheduled over the steeper sections of Sherman Hill due to the train's relatively high power-to-weight ratio which allows the train to better deal with tough grades while heavier freights like manifests and unit trains use the lower-graded sections for an easier climb given their low power-to-weight ratio.
Anyway I've got the brake difficulty cranked up to "Hard" and I make good time through Red Buttes making either 60mph or pretty close to that all the way up to Hermosa (Main track 3 is actually pretty flat until you get out of Red Buttes where the grade gets up to 1.6%, and even then because of the momentum your train's picked up traveling at 60mph up to that point your train doesn't slow much at all up to Hermosa). I slow down for Dale Junction, power my way up to Sherman Hill Summit and ride my dynamics down to Buford. I haven't been out of Buford for too long when I get a notification that the PCS has been tripped and the train is going into Emergency. "Well that's odd," I think, because I never got a notification from the Alerter or anything, and I don't even know if this loco has an Alerter in TS2018. Not wanting to lose time on this test run, I put the brake handle into "Emergency" then into "Release" in order to reset the PCS and release the brakes before the train has a chance to come to a complete stop.
Mind you the brake setting is set to "Hard" on this run, and since my train is 111 cars long I'm expecting that it's going to take a while for the air in the brake line to recharge. Surprisingly, it recharges very quickly. "That's also odd," I think, but again wanting to make up time I move on.
I make my way to Granite and not long after I pass through there I glance down at the track monitor. If you've driven 100+ car trains in TS2018 before you know that the train barely fits into the track monitor because it's so long. What I see in the track monitor is a highly-abbreviated freight train. I stop the train and switch to external view 1 to count the cars. Out of the original 111 cars that I had leaving Laramie only 15 were left. Obviously the tail end of my train separated somewhere up the line, so I turn on the 2D map and retrace my steps to find out where the rest of the train is. I finally spot my lost 96 cars somewhere on the main line between Buford and Granite somewhere in the vicinity where the PCS tripped. When I reset the PCS I wasn't paying attention to the track monitor, so I don't know when exactly my train separated.
In my experience in Train Simulators since the days of MSTS, train separations are a very rare occurrence for me. The last time I had a train separate was on Cajon Pass back in 2012 with another stack train powered by 4 BNSF ES44ACs from the BNSF ES44AC & SD40-2 pack way back when that was new. Because it's so rare I stopped looking for them.
So here's what I know: my train separated somewhere between Buford and Granite, and my train went into "Emergency" around the same place. What I don't know is what came first: the separation or the Emergency brake application. In real life if the train separates the train goes into Emergency and once the train comes to a complete stop the crew has to inspect the train and if a coupler has broken then the conductor has to replace it, then the train is put back together, the brakes are recharged, and the train continues on its way. As far as I know that's not possible in TS2018, but this is with Mrennie's advanced braking script and I don't know just how far the simulation goes in the script.
So did my train separate and cause the PCS to trip, or did my PCS trip and somehow the train separated after I reset the PCS and began accelerating back to track speed? I dunno. Interesting to think about, though.
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I'll try again later, moving one of the units to the back as a DPU to see if that helps to even out the train forces. 
