The info for the loader/unloader is saved to the session, not the route so every time you edit the route you lose the info. Therefor either (a) don't set industry tracks up till right at the end of the route-building effort - or - (b) only ever edit the route by entering via 'Edit Session' that way you maintain the data.
 
The problem with (b) is that sooner or later you forget, and 'Bam' - all gone...
 
Andy