Okay, next is set faulty dependencies = true, missing dependencies = true, has warnings = true, see what that turns up starting with D.
If that don't find it, go into surveyor, set the content filter for category locomotives, see if it still does it. If not, set for category rolling stock and see if that does it. Idea is to narrow it down, is it a loco or a coach/wagon?
Next step, set the content manager filter for location = local, category (for this example, assuming rolling stock is the problem) rolling stock. Select all rolling stock starting with the letter D (Click the top and SHIFT click the bottom), right click, select Enable/Disable so all rolling stock starting with D is disabled. Back to surveyor, see if all categories are okay. Back to content manager, select the top half of the ones you have disabled, enable them so they show up in the list again. Back to surveyor, does it do it? If yes, back to content manager to disable half of the half you enabled, if not then enable half of the half that's still disabled. Eventually you'll close in on the culprit.
