Sadly I still have this error with v0.3.20 when flame tumblers tries to attack. I tried mining a vehicle and place it again to get around possible migration issues. Same result. I'm using flamethrower ammo.Error while running event aai-programmable-vehicles::on_tick (ID 0)
__aai-programmable-vehicles__/util.lua:182: attempt to perform arithmetic on field 'x' (a nil value)
Bullets (cars and chain gunners) have been fixed and works fine. Great work. In fact I want to praise you for not just some great mods, which adds a lot to the game, but also the way you handle bug reports. Often people take for granted that people who wrote some code also fix the bugs "because they know the code". However speaking from experience bugfixing can be anything from trivial to more difficult than writing the code in the first place. Sometimes even figuring out the cause of a bug can be an issue, which takes skill and time. I have seen modders (not factorio), who wrote decent mods and then fail to fix bugs due to lack of skills while other doesn't care much after they released whatever they made.
I want to take this opportunity to praise your responsiveness to bug reports as well as providing fixes for reported bugs quite fast.