In the last two versions I downloaded of the latest experimental (builds 3885 and 3888), I’ve received regular errors on world load specifying “Invalid spawn location (no CARGO vpart) in {Beetle|Bubble Car} (-2,1): {8%|3%}”. A quick check of the cars.json file (\data\json\vehicles\cars.json) reveals that this is tied to the spawn location of the trunk items, in both cases the jack or wheel, respectively on lines 743 and 822. I’m not positive on why these errors began appearing as it appears that nothing has changed in this file, but these items and probabilities declared in these lines appear to be concurrent with the immediately preceding item declarations (“car_kit”, which defines both the jack/wheel “or” as well as several other items), and removing the lines causes no immediately-apparent issue. If these items are specifically intended to be spawned independently of the car_kit declaration, it may be practical to at least redefine the location so that it spawns in a cargo area, likely a trunk.
EDIT: Corrected first build number: it was build 3885 rather than 2885.