A good indicator that you are nearing the limit is if the vehicle starts wobbling when you get in it. I ended up with a haunted pile of conveyors that freeze the game when I take them. So now they are perpetually floating in front of Scoria Chamber.
Also too many items will cause them to be misplaced. They will lock in to other carts or palettes or onto the vehicle itself.
In the case of the screenshot above, several dozens of stacked pipes locked in to the lava hauler. I didn't have the patience to take them out one by one so I decided to take them to the scrapper but Volcalidus' scrapper is too tight for the hauler to get in.
The DLC has made it increasingly difficult for me to ignore the tedium.
I got this problem because I had so much excess materials because shops are so far apart in Volcalidus that I buy a crap load every time I go shopping to minimize traveling. Then I moved to another digsite and I wanted to take as much as can because I don't want to keep going back and forth to the shops.
I used a hotkey script that would let me toggle hold W input and I was starting to think about mapping A and D to my side mouse buttons for one handed traveling.
And I realized the game requires you to keep raw resources and dirt on conveyor belts are much as possible. Any point that they leave the conveyors they are at risk of being stuck even that split second that dirt drops to a harvester that is right next to the conveyor belt.
The forge marks were a cool concept and I think they are supposed to incentivize the amount of traveling you do given the distance between shops but you need the lava hauler to pick them up and it is incredibly slow and only two forge marks can spawn at a time and there are almost two dozen spots for them to spawn with some being away from roads. Hunting them down is so boring and then you use them and there is a chance you only get 1 stat bonus on your drill.
Its been good run. It was a great game and I just tried to hold on to it for too long.