I love how you've tried to cordon off the area, lmao. Great stuff.
It's 99% probably caused by either 1. too many vehicles in that area or 2. invalid vehicle mods.
1. The game can only handle loading a certain number of vehicles and different vehicle models at once. I'm not sure of the exact limits but around 70 different vehicle models seems to crash the game. I have applied fixes in the past to try and remedy this by reducing the number of vehicles and models that can spawn in an area. It is currently configured to only allow 70 vehicles to be spawned in a 400 radius. I really don't want to have to lower this any further as it's going to make the world very sparse in terms of ambient/static vehicles, but I guess I will take it down to 60 vehicles within 450 radius for now and see how it goes.
2. Every vehicle mod/component such as spoilers, exhausts and so on has an ID. For example 10x nitro is component ID 1010. Nitro can be added to almost any vehicle without any issue. Some vehicle components however are designed for either one specific vehicle (e.g. 1034 is an exhaust only compatible with the Elegy). If a component is added to a vehicle with which it is not compatible, it will crash the game. Some players download mods for their vehicles which give them different components to add in transfender, which are compatible with their mod but not compatible with other players. When they add the component and drive near other players, those other players will crash as their game is trying to load an incompatible component for that vehicle.
I added protection against this recently but have been unable to fully test it. I need to do that.
1. is generally the cause here though. Even though I've set a limit for how many vehicles can be in an area, players can drive more vehicles into that area. The only solution is to respawn the vehicles. Vehicle respawn time is currently set to 10 minutes (excluding personal/job vehicles which don't despawn) and I can't really make it any lower. Admins on the server can respawn all empty vehicles, which generally fixes this situation.
One solution I can think of is once a minute or so the server can check areas to see if there are too many vehicles there, and if so it can respawn the oldest occupied vehicle or something.
That's all I know. I'm not really sure what the ideal solution is.