Sure thing.
Playing around, it looks like "Drivability" value is the cause in this case. If it falls out of bounds (Below 0? or "inf") it messes up the calculation and brings up anomalies. Also in track testing, where it doesn't register correctly and causes game crash (sorry, i haven't taken the error dump).
And i thing that that goes back to the "low speed steering" section, when it also tends to loose graphs and go out of bounds when messing with tires to unreasonable levels. I see it has improved in the latest release though.
I'm a bit struggling with the game mechanics point of view aswell, on how and what causes the other in the game engine. That is my fault that i haven't dwelled too deeply into it.
If i can assist in any way, let me know
-edit- I tried to re-produce the behaviour and managed to get error on the graphs side. Drivability is "nil" and Markets gave expected result. The issue, this thread started with, seemed to be some borderline calculation that messed up the markets aswell. But i rememeber the "Drivability" stat was... weird
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Lua Error:
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tolua++ dbcall failed!: [string "--client\functional\TrimDesignerWindowGraphs...."]:903: attempt to index a nil value
-edit2-
I tried to re-produce it again with a 2015 era car. I can confirm that "Drivability" is "inf", tires are embarrassing, graphs are not showing, although the error mentioned above did not pop up. Market stats are overwhelmingly positive and cannot tracktest, cause tires would blow.
-edit3-
Track-test failure occurs when car is incapable of reaching 100km/h or 120km/h (again, unable to calculate nil valjue)