Took a run on my Columbia River Route in one of my favorite Locos, the USRA 2-8-8-2 TS12 version. Got about 2/3 of the way though , and was waiting at a siding for an AI train to pass, and my water level dropped to zero and slowly so did the steam pressure. At that point, I was stuck.   Checked the level in the Tender, and there was no water at all, I had run this tender bone dry, and this run is probably under and hour.  Now I looked at the same tender prior to running the session and the max  capacity was only 5,000 gallons.  Looked at another GN 2-8-8-2  LOCO tender I have ,  and it held a max of 46000 Gallons, and was loaded to 35,000 at the start. So, I need to edit the config file for the USRA tender and change that water quantity , which I did. I hit commit, went back to the session, and I still have 5,000 gallons.  
.  Checked everything on both tenders, and can't figure out the problem.  Finally, I deleted the low water tender in the session edit , and just reinstalled it, and problem solved. So when you make a change like that, even though you commit the change, if you don't delete and reinstall the item, the changes won't  take effect.