I ran into a similar situation a couple of times. My issue was related to a badly scripted asset such as an industry the last time. Another time it was caused by a corrupted mesh. I had some symptoms before that hinted on an issue such as spikes that appeared on top of the building followed by really, really long shadows that flashed and radiated out of the building. I ignored it at the time because I was working on something else and when I upgraded, it crashed the route.
Scripted assets generally don't do any harm in Surveyor because the scripts are not active. It's in the sessions where they become an issue and this is why the crashes occur there.
Remember, you need to run a DBR after a crash to clean things up because not doing so can lead to further crashes as I've found out the hard way.
You can try checking the Client Logs and see who was loaded at the time of the crash. Enable timestamps in the log by right-clicking on the column at the top. You can then check your system clock and get a rough time when the crash occurs. To be honest, this worked twice for me and I'm not sure if you'll have any more luck than I did.
If this doesn't work, you need to do a more drawn-out method using the process of elimination.
In Content Manager, show the session dependencies. Using that same view, remove built-in and packaged using filters such as packaged set to false.
Highlight the remaining content.
Click on Content on the menu bar.
Click on Disable.
Start your session.
Select your route and session.
Yes, you will have missing assets. Ignore that and don't run delete missing assets from the route!
Start the session. It may not run due to missing locomotives!
Does it crash?
If nope, close Trainz back to your desktop.
Open up Content Manager.
At the Installed filter, expand that by clicking on the small arrow.
Click on the + sign (plus-sign) to add another line.
Change that to Enabled and change True to False.
Highlight 100 or so assets located in the window.
Click on Content on the menu, and then click on Enable.
With your content enabled, repeat the run and wait for a crash. Remember to run a DBR in between if there's a crash.
Go back to Content Manager with that content enabled and enable another 100 or so assets.
Repeat the run cycle again.
Eventually, you'll run into the asset that causes the crash. Disable this last group of assets you enabled and enable a smaller group of them. If it doesn't crash in this cycle, repeat the enabling a few at a time until there's a crash. With this last batch, you need to work with yet another smaller chunk of assets until there's a crash.
Hint: The bad asset is usually the last one you've enabled and this is directly correlated to the Laws of Murphy.
