• Version? 41.73
• Singleplayer/Multiplayer? Tested only in MP
• Host or dedicated? Both
• Mods? CheatMenu
• Old or new save? Both
• Reproduction steps:
1. Use whatever tool you have on hand to give a vehicle a really low engine power, like 1hp.
I used CheatMenu, then a little custom mod, to the same effect.
2. Drive forward, should drive normally
3. Try to reverse. Should be unable to
4. revert the engine power, now reverse works as normal
If I root around in CarController.control_ForwardNew(), which I think is the code handling forward momentum, I notice the EngineForce is initially set to vehicle.getEnginePower(), but then is immediately overwritten with vehicle.getScript().getEngineForce(), at least when looking at a decompiled version. I suspect this is the cause of the vehicle being able to drive forward no matter its current "enginepower", and why enginepower reductions from poor engine quality simply don't do anything:
Its being overwritten by the default value in the vehicle script