Just tried to do an Amtrack reverse loop service on Boston-Providence. I got all the way through the loop, and was on the straight when I got a "Service Failure: Derailment". I didn't go through any red signals, and my speed was 4.7MPH in a 5MPH speed limit, so what gives?
Do you have disable derail junction unchecked in settings? If you don't select it, if switches aren't aligned properly, you can derail. Did you set the switches properly?
Wasn't this the one where you drive your train into a building? Although I thought that was "fixed." Another possibility is that another train hit your train. The other trains in that area can and do ignore signals and you have to watch out for them.
Like above said, what were the signaling systems telling you and what the hud signals are telling you. Check that it is safe to do so before moving. Just because permission is granted doesn't mean it is safe move.
I've had this and only realised what was happening when I drove the loop from the external camera zoomed right out. As you get just over half way round the loop, after the crossing I think, there's a southbound train that's come out of Boston that just spears straight into the side of you. Your signals are all green, nothing on the cab signals or HUD to say you should have stopped. So now I either go a bit faster around to beat it (naughty I know) or just stop by the crossing and check the map for any southbound traffic. Maybe something similar with you even if it's a bit further on the loop?
Could have been that, I was in the cab view. All signals I passed were telling me to proceed both external and in cab.