Here is what I do: A simple turntable should have at least two stubs (short pieces of track that connect to your main track). Joint the track to one of the stubs and leave the other empty or with a short invisible track with an invisible signal. This other dead end should have a trackmark, and you can call it TT0. Adjust the radius of this track mark so that the main bogie of the loco is still over the turntable bridge when arriving. Go to driver and issue a command for the loco to drive (or navigate TO) to this TT0 trackmark. And see how it works. Then you could set the Turntable to automatically turn to a desired position if properly set. It works quite well.
