My bet is that your paths are way off.
Here is a useful trick.
Make your ships.tbl file, with the model with no paths.
In FRED2, go to menu, View & enable show paths. All the red lines u might see are the actual paths, but for your no path model, there should be none. You can also View dock points and fighter bay paths by enabling View Dock points.
Now place your Model at coordinate 0.0.0 and don’t rotate it: (Note: you right click on your model, select orientation and position, and make a manual typed position at 0.0.0 as it will be hard to place it there with mouse.
In FRED2: Now save the Mission under some name but don’t close FRED2. This will come in handy later.
In FRED2: Select you model, zoom, and now press k to find for example Turret01, in fact this example requires it to be Turret01.
Open PCS open your model “FROM” the fs2/data/models directory
In FRED2 place two waypoints, and place them as they where the start and the end of the path for Turret01:
In PCS->paths: ADD path and name it $path01( or whatever number), and give the path the parent Turret01
In PCS->paths: ADD TWO VERTEXES ( and only two, FS2 will only look for two)
In FRED2 Note the coordinates of the waypoint closest to Turret01
In PCS->paths: put these coordinates into Vertex01 (FS2 will look for this as the Vertex Nearest Target Subsystem)
In FRED2 note the coordinates of the waypoint farthest away from Turret01
In PCS->paths put these coordinates into Vertex00
In PCS->Regarding Radius for the two vertex’s, open another instance of PCS and open any original POF file from Volition, but similar to your model, and simply copy those values, from this instance of PCS to your models Instance of PCS.
In FRED2 now save your mission, and your models paths should magically appear, as FRED2 is Reading all models in the mission, each time you save the mission.
You might not see it, because it is being covered by the waypoints, but it should be there, just remove the waypoints and you can tell, or rotate around the model, and the red path should flicker through the purple waypoint. This way you can tell in a moment if the path is typed in Wrong in PCS, like if you forget to put “minus” in front of a number or something similar.
A good piece of advise is to Keep good notes on which $pathXX`s leads to Which Turret, as you might assign to wrong turret to a path. And once you do that a couple a times, well then it is hard to keep track of what $path belongs to What turret as FRED2 don’t tell path names.