thank you brumi for trying and reporting those errors
- error 1 was already found and fix, a stupid one
- error 2 is more problematic and need more handling to fully correct the "why it happen", for now i already fix the "don't crash if it happen" anyway i've add a check to try to order a vehicle to goes to a "null" homedepot.
- error 3 worry me a bit more, as the no order solve depend on the error 2 (no order, trying to set new ones), but the train running alone is a bit more sad, as i have already think it could happen (running low on money after building the train and 0 cash to pay the wagons), and the AI should have catch it, and instead of starting that empty train, should have sell it. I suppose i didn't do it as good as i think
For the newgrf, i didn't test every grf that exist, but i have test some of them, and you could see the AI should handle them pretty well (the ones i test, like eGRVTS).
For the Aviators, if it's av8 something, my AI and all AIs i've saw, and even for human player, it looks impossible to make money with the costs and running costs those aircrafts have, i really like the drawing and the details of the aircrafts, but the settings ruin totally the fun of this grf (for me at least). I'm not sure how i should handle this one, except my generic handling of newgrf engine doesn't work with it, but i think it comes more from the newgrf maker than a "poor" handling of my AI.
In fact, the only one that bug me seriously was the Ikarus Set that report articulated vehicle as non-articulated ones.
Anyway i could confirm none of the errors you report comes from newgrf usage as you could get them too without them.
I didn't test yet non engine newgrf (stations or industry stuff like that).
Here's an update version with many fix and the error 2 (half-fix), that should run a bit better before crashing
I named it 155a, not as alpha, even it could fit nice, but just as i need a different name so people catch it's an update one.