When you build on ore, the entity is destroyed that same tick, then rebuilt the next tick since your mouse button is still down. This usually results in 3-5 entities being destroyed, instead of just one. Since it can be hard to see if a single tile of ore remains, especially when covered in biter corpses, can you somehow fix this? Perhaps wait a couple of ticks before destroying the entity, or preventing the player from building for half a second. Or even better: Just prevent building on ore, instead of destroying the entities built there.