Under normal circumstances, the 3D printer will open the nozzle for a long time when it stops printing, which will cause the consumables to carbonize and block the nozzle. There are many other reasons. Now many nozzles are made of copper, and the strength is not high. In the case of leveling mistakes, it is easy to cause the nozzle to hit the hot bed and cause the nozzle to deform, which eventually leads to plugging.
For the most part, it is recommended to use a 0.5mm drill bit (depending on the diameter of the orifice) through the spray head, which basically saves most of the spray head.