Very occasionally if you have heavy logistic bot congestion a logistic bot will crash.
A construction bot will automatically retrieve the dropped cargo, it is not lost.
This means logistic bots are best used for higher value items like engines or power poles, using them for low value items like ore and copper wire is OK but less resource efficient.
The goal is not to stop your from using bots, but to provide a small incentive to use belts in some situations late-game.
The crash rate is configurable (down to near-zero).
With the default settings:
Bot-based item malls are totally fine.
100% bot-factories are still viable but need maybe 1% extra resources - if that. (This percentage may vary based on the mods used.)
Bot-train ore unloading is viable but not ideal.
Bots carrying ore from distant lands when you should be using trains is where things can become unsustainable unless you reduce the crash rate.
If you play with expensive recipes enabled or on marathon mode then you may need to be a little more careful of excessive bot use, or you could just reduce the crash rate.