I only started with this pastime in 2017.
I purchased a few routes from MLT as I was familiar with the geography. I really like the routes.
I finally began to pursue the Activities and found a Track error in the London Yard in Niagara Corridor (Dundas Sub). On Race Course Yard Track 3, near the West end, I have a bad Dynamic Track joint that causes derailment crashes . It is obvious under Activity CN 584 London Switcher which uses that section of track. I can complete the activity if I avoid that section.
If I repair the track with Route Editor, the track is fine, but nearly all the Activities 'break' and the cars and engines start acting jumpy.

Is there a track database repair step to do somehow??

I have installed this on 4 different PC's, Win XP, Win7 and Win10. It always has the same problem. The latest Niagara upgrade (6) has same effect for me.
My setups have the latest XTracks and Tsections, I can find.
I realize, often Routes and Activities have errors in them, and I have had some success finding and repairing them to work for my use. However, sometimes these things stall me.
I can post a screenshot of the problem if that helps.
Any advice?