Which version did you install, TANE or Trainz 2019 revamped version? If you have not tried the revamped version, I would delete all the faulty dependencies and the route, rebuild the data base and then install just the revamped route.
When you installed the files did CM at any point give you the message, asset already installed? I have a feeling that some of the assets that came with the file are faulty. For the dependencies that you had before that are now faulty, I would erase them and then redownload from Content Manager.
Can Surveyor be used in Multiplayer so multiple users can build and edit the same route at the same time? Yes.
If yes, can we use our own custom content (locos, rolling stock, tracks, scenery) in these sessions? I believe that is a no. The is no way for the app to know whether all participants...
I just tested TLR with just two boxcars loaded with general goods and a gp38 not attached. The dispatcher did assign the gp38 to couple onto the two boxcars and deliver to a multi-industry new that accepts general goods.
It was a 60 mph passenger and 40 mph freight line more recently than that. I was on a couple of excursion trains One to Rotterdam Junction and then another one to Adams MA in the 80's. The Fitchburg Route tracks were better than the B&A back then.
If you don't want to test new features, you can avoid the Beta patch stream.
I personally do not like the imposter system. When ride a train I like to zoom out and look at distant objects. With the imposter system the distant objects look terrible.