Williamg - Which portal (Name and KUID) are you using? There were problems with portals in Service Pack 2 that were supposedly fixed in this new build, SP3.
One of the issues encountered was indeed related to reversed vehicles in the named consists - but that was fixed (we thought).
I have tested this extensively over several beta builds and the latest build 111951 again today based on your comments above and cannot reproduce those earlier derailments, even with very long multi-loco consists with reversed bankers, etc.
The portals that work for me are: <kuid2:96914:22000:2> Portal Basic Short and <kuid:-25:1264> Portal.
I have been unsuccessful in ever getting the most recent update to Portal Basic (HP) to work successfully in TRS19 as the 2 latest versions bring over pre-included (faulty) consists in its configuration files.
My test today did however show considerable jerkiness of a very long consist emanating from a portal (<kuid2:96914:22000:2> Portal Basic Short ). This particular consist has 5 or more leading locos with some facing forward, others reversed, and 46 or more container flats plus a reversed locomotive banking at the rear.
Despite the jerkiness, it issued without derailment and then happily proceeded to complete its assigned schedule.
Please send in a Bug Report outlining the repro steps/ methods required to derail your portal emissions/ consumption using this form
https://n3vgames.typeform.com/to/xRdryu so we can get QA to sort out this issue once and for all. Cheers and thanks. PC.