OK, you asked... long list
off the top of my head;
1) It reads some of my sprites a little weird so it will set the train off center on the tracks. especially my bogie's.
You WILL LOOSE all of the following items from my trains:
2) bogie's, (unless you re-enable them them in VC. then they are off center, see above)
3) any custom sounds,
4) "locked direction" so the car might flip "backward" from intended,
5) "end of the line" code to turn the "front" in direction of travel ( to prevent a train/tram from "running in reverse" at the end of the line instead of the driving "cab in the front".... or ....the pantos in the wrong configuration; this is for single car trains, MU's, or trains where every car is powered )
6) custom cargo's, (also custom cargo configurations where you mix different cargo's) ... Note: in addition, this can also cause some of my multistate cars to spin in circles if you change what cargo's I had set.
7) If you make a "set of cars" in one dat (not an MU. where it builds a different car each click. like the official "Shinkansen" add-on ); VC turns it into a single MU where you get all the cars at once and looses all the cargo settings.
It messes up something with narrow guage and road vehicles. I forgot what it was. I think it puts the wrong sprites for steep slopes? (anyone remember?)
I am probably missing a few more bugs.
I think You might see the picture. VC is OK for most new items. VC for Modifying an existing one, not good.
I don't think I have used VC or MSTS2lomo in a long time. I do it all by hand. so my stuff gets really messed up by VC.
PS. My stuff does work fine with "Wrapper for locotool" or "locowrapper" to change reliability and obsolete dates.