I've spent the whole weekend trying to solve the 'disappearing bulk products' problem - many of my waggons are affected. While the bug is repaired in TS12, older versions of Trainz are still affected. As Dampfloker suggested me there is only one way to solve the problem - all bulk loads must be in one load in config. This unfortunately leads to other 'physical' problems like overloading a waggon (62000 cubic meters of coal is twice lighter than sand).
My friends from Polish Trainz Team discovered a workaround for this and it goes as follows:
- open the waggon preferences window
- load your desired bulk product
- confirm and close the prefs window (the load disappears)
- open the load window, delete the loaded but invisible product with 'x', then close the load window with also 'x' (like if you don't want the changes) not with the 'confirm' button
- now the product miraclously goes back!
I'm sorry for writting in English, it would be great if anybody translated it into German
Wojtek