This is to repair the track object issues where the track isn't recognized as a valid track and the objects won't connect to them.
Since you have run a DBR and EDBR multiple times, I recommend checking faulty assets in Content Manager. There will be many shown, and you need to select them all. Once selected, right-click and choose View errors and warnings.
A small window will open up showing anything that's broken, or not. After a DBR, this will usually clear any faults from the database. You will have to close this screen and check for Faulty assets again to refresh the screen.
If there are any faulty assets remaining, these will need to be downloaded again.
Check for updates. There has been a number of updates recently since the patches have been released and these have resolved some of the asset errors since the updates.
It is possible that your session is corrupted for some reason causing the program to crash, or it could be some script that's causing the crash.
You can try a couple of things.
1) Click on the Launcher and then Trainz Settings.
2) Click on the Dev tab
3) Click on Show script exception notifications.
What this will do is bring up a red bug symbol if there is an issue with a script or script(s). By clicking on this red bug, it will show various scripts that have errors, and if you click on those, they will expand showing the actual line or lines that cause the problem.
Knowing which script is causing the problem will help you then track down the asset or assets that are causing the failure.
You will have to run your session in order to see the script failures.